> #odeplot
> with(plots):
> lambda:=0.001;mu:=1/14;

                           lambda := 0.001


                              mu := 1/14

> ODE1:=diff(x(t),t)=-lambda*x(t)*y(t);

                          d
                  ODE1 := -- x(t) = -0.001 x(t) y(t)
                          dt

> ODE2:=diff(y(t),t)=lambda*x(t)*y(t)-mu*y(t);

                    d
            ODE2 := -- y(t) = 0.001 x(t) y(t) - 1/14 y(t)
                    dt

> ODE3:=diff(z(t),t)=mu*y(t);

                             d
                     ODE3 := -- z(t) = 1/14 y(t)
                             dt

> SYS:=[ODE1,ODE2,ODE3,x(0)=900,y(0)=10,z(0)=90];

          d
  SYS := [-- x(t) = -0.001 x(t) y(t),
          dt

        d                                      d
        -- y(t) = 0.001 x(t) y(t) - 1/14 y(t), -- z(t) = 1/14 y(t),
        dt                                     dt

        x(0) = 900, y(0) = 10, z(0) = 90]

> ans:=dsolve(SYS,numeric,range=0..15,initstep=0.1);

                 ans := proc(x_rkf45)  ...  end proc

> XvsT:=odeplot(ans,[t,x(t)],t=0..15,color=blue):
> YvsT:=odeplot(ans,[t,y(t)],t=0..15,color=red):
> ZvsT:=odeplot(ans,[t,z(t)],t=0..15,color=green):
> YPvsT:=odeplot(ans,[t,lambda*x(t)*y(t)-mu*y(t)],t=0..15,color=plum):
> display(XvsT,YvsT,ZvsT,YPvsT);
> for i from 0.0 to 15.0 by 0.1 do ans(i); od;

            [t = 0., x(t) = 900., y(t) = 10., z(t) = 90.]


  [t = 0.1, x(t) = 899.062166438715734, y(t) = 10.8633635192417799,

        z(t) = 90.0744700420424351]


  [t = 0.2, x(t) = 898.044520218485558, y(t) = 11.8001141100646123,

        z(t) = 90.1553656714498999]


  [t = 0.3, x(t) = 896.940487576500572, y(t) = 12.8162803136165451,

        z(t) = 90.2432321098831949]


  [t = 0.4, x(t) = 895.742985822509922, y(t) = 13.9183543223176738,

        z(t) = 90.3386598551724944]


  [t = 0.5, x(t) = 894.444403835698608, y(t) = 15.1133093223940023,

        z(t) = 90.4422868419074178]


  [t = 0.6, x(t) = 893.036559513875886, y(t) = 16.4086373968666308,

        z(t) = 90.5548030892573905]


  [t = 0.7, x(t) = 891.510671296842020, y(t) = 17.8123746665611869,

        z(t) = 90.6769540365967544]


  [t = 0.8, x(t) = 889.857330159109324, y(t) = 19.3331257994047548,

        z(t) = 90.8095440414858786]


  [t = 0.9, x(t) = 888.066454271867769, y(t) = 20.9801037303432274,

        z(t) = 90.9534419977892128]


  [t = 1.0, x(t) = 886.127275265593993, y(t) = 22.7631410462340718,

        z(t) = 91.1095836881719521]


  [t = 1.1, x(t) = 884.028291079781524, y(t) = 24.6927304871822990,

        z(t) = 91.2789784330363148]


  [t = 1.2, x(t) = 881.757248245719666, y(t) = 26.7800392673035646,

        z(t) = 91.4627124869765993]


  [t = 1.3, x(t) = 879.301118109095000, y(t) = 29.0369279508123697,

        z(t) = 91.6619539400924453]


  [t = 1.4, x(t) = 876.646062862339022, y(t) = 31.4759777671105141,

        z(t) = 91.8779593705505420]


  [t = 1.5, x(t) = 873.777440700101806, y(t) = 34.1104832458545530,

        z(t) = 92.1120760540432997]


  [t = 1.6, x(t) = 870.679775739577508, y(t) = 36.9544738119763778,

        z(t) = 92.3657504484461498]


  [t = 1.7, x(t) = 867.336768173229415, y(t) = 40.0227007890557900,

        z(t) = 92.6405310377147373]


  [t = 1.8, x(t) = 863.731305622510149, y(t) = 43.3306207154322891,

        z(t) = 92.9380736620574056]


  [t = 1.9, x(t) = 859.845465276046866, y(t) = 46.8943857702815805,

        z(t) = 93.2601489536713473]


  [t = 2.0, x(t) = 855.660570415389088, y(t) = 50.7307869986001521,

        z(t) = 93.6086425860105891]


  [t = 2.1, x(t) = 851.157222011737872, y(t) = 54.8572134589971796,

        z(t) = 93.9855645292647210]


  [t = 2.2, x(t) = 846.315365089860392, y(t) = 59.2915844921772006,

        z(t) = 94.3930504179620442]


  [t = 2.3, x(t) = 841.114392896880304, y(t) = 64.0522434268334564,

        z(t) = 94.8333636762863677]


  [t = 2.4, x(t) = 835.533230570643354, y(t) = 69.1578658915471323,

        z(t) = 95.3089035378096696]


  [t = 2.5, x(t) = 829.550484918597362, y(t) = 74.6273152979967591,

        z(t) = 95.8221997834060488]


  [t = 2.6, x(t) = 823.144616255786786, y(t) = 80.4794652928400041,

        z(t) = 96.3759184513733942]


  [t = 2.7, x(t) = 816.294096421282006, y(t) = 86.7330412283157273,

        z(t) = 96.9728623504021244]


  [t = 2.8, x(t) = 808.977659446653205, y(t) = 93.4063789649349588,

        z(t) = 97.6159615884117784]


  [t = 2.9, x(t) = 801.174559438764504, y(t) = 100.517160780799685,

        z(t) = 98.3082797804353703]


  [t = 3.0, x(t) = 792.864814088217713, y(t) = 108.082182607544481,

        z(t) = 99.0530033042376061]


  [t = 3.1, x(t) = 784.029580170900658, y(t) = 116.116990439756222,

        z(t) = 99.8534293893432334]


  [t = 3.2, x(t) = 774.651475592019096, y(t) = 124.635556212967913,

        z(t) = 100.712968195013318]


  [t = 3.3, x(t) = 764.714920679581382, y(t) = 133.649959843644864,

        z(t) = 101.635119476773539]


  [t = 3.4, x(t) = 754.206621929417338, y(t) = 143.169921413844946,

        z(t) = 102.623456656738000]


  [t = 3.5, x(t) = 743.115924165301976, y(t) = 153.202452828574593,

        z(t) = 103.681623006123686]


  [t = 3.6, x(t) = 731.435218456629627, y(t) = 163.751486075544704,

        z(t) = 104.813295467825611]


  [t = 3.7, x(t) = 719.160464015402452, y(t) = 174.817375387169249,

        z(t) = 106.022160597427927]


  [t = 3.8, x(t) = 706.291525977222704, y(t) = 186.396567979557858,

        z(t) = 107.311906043219565]


  [t = 3.9, x(t) = 692.832553504204838, y(t) = 198.481271153585509,

        z(t) = 108.686175342209594]


  [t = 4.0, x(t) = 678.792416932567789, y(t) = 211.059053663085848,

        z(t) = 110.148529404346220]


  [t = 4.1, x(t) = 664.184964726459042, y(t) = 224.112602050825898,

        z(t) = 111.702433222715100]


  [t = 4.2, x(t) = 649.029193998880372, y(t) = 237.619588441694645,

        z(t) = 113.351217559424838]


  [t = 4.3, x(t) = 633.349572377594654, y(t) = 251.552407746981970,

        z(t) = 115.098019875423148]


  [t = 4.4, x(t) = 617.175938995433966, y(t) = 265.878302588366068,

        z(t) = 116.945758416199751]


  [t = 4.5, x(t) = 600.543432641721893, y(t) = 280.559447378615687,

        z(t) = 118.897119979662889]


  [t = 4.6, x(t) = 583.492476892221362, y(t) = 295.553026394092171,

        z(t) = 120.954496713686396]


  [t = 4.7, x(t) = 566.068697193387834, y(t) = 310.811356320518939,

        z(t) = 123.119946486092942]


  [t = 4.8, x(t) = 548.321855775493986, y(t) = 326.282975850765012,

        z(t) = 125.395168373741256]


  [t = 4.9, x(t) = 530.305722562683400, y(t) = 341.912779014689192,

        z(t) = 127.781498422627151]


  [t = 5.0, x(t) = 512.076865496674827, y(t) = 357.643263864677692,

        z(t) = 130.279870638647310]


  [t = 5.1, x(t) = 493.696420726302164, y(t) = 373.412800895229680,

        z(t) = 132.890778378468070]


  [t = 5.2, x(t) = 475.226942037349772, y(t) = 389.158779314065042,

        z(t) = 135.614278648585184]


  [t = 5.3, x(t) = 456.730859776741453, y(t) = 404.819155315608327,

        z(t) = 138.449984907649905]


  [t = 5.4, x(t) = 438.270480852540231, y(t) = 420.332452080990379,

        z(t) = 141.397067066468964]


  [t = 5.5, x(t) = 419.907988733948684, y(t) = 435.637759778046643,

        z(t) = 144.454251488004558]


  [t = 5.6, x(t) = 401.704514062920794, y(t) = 450.675653984246764,

        z(t) = 147.619831952832299]


  [t = 5.7, x(t) = 383.718755121640470, y(t) = 465.389556133115888,

        z(t) = 150.891688745243755]


  [t = 5.8, x(t) = 366.006498920136664, y(t) = 479.726177190909594,

        z(t) = 154.267323888953570]


  [t = 5.9, x(t) = 348.619160025425742, y(t) = 493.636950102614946,

        z(t) = 157.743889871959311]


  [t = 6.0, x(t) = 331.603767070009724, y(t) = 507.078043086695004,

        z(t) = 161.318189843295244]


  [t = 6.1, x(t) = 315.002944698390479, y(t) = 520.010369106647772,

        z(t) = 164.986686194961350]


  [t = 6.2, x(t) = 298.854460011347725, y(t) = 532.399924333294052,

        z(t) = 168.745615655358164]


  [t = 6.3, x(t) = 283.190772029504160, y(t) = 544.218221492740440,

        z(t) = 172.591006477755883]


  [t = 6.4, x(t) = 268.039062575645971, y(t) = 555.442219660835803,

        z(t) = 176.518717763518310]


  [t = 6.5, x(t) = 253.421231090309817, y(t) = 566.054316228849756,

        z(t) = 180.524452680840056]


  [t = 6.6, x(t) = 239.353904645770086, y(t) = 576.042335123154884,

        z(t) = 184.603760231074829]


  [t = 6.7, x(t) = 225.848860906271909, y(t) = 585.399001581510333,

        z(t) = 188.752137512217785]


  [t = 6.8, x(t) = 212.913196077408429, y(t) = 594.121720482093678,

        z(t) = 192.965083440497892]


  [t = 6.9, x(t) = 200.549783861744942, y(t) = 602.212132518064209,

        z(t) = 197.238083620190877]


  [t = 7.0, x(t) = 188.757484495111043, y(t) = 609.675885811004946,

        z(t) = 201.566629693884352]


  [t = 7.1, x(t) = 177.531527008394391, y(t) = 616.522205689511793,

        z(t) = 205.946267302094071]


  [t = 7.2, x(t) = 166.863931528453463, y(t) = 622.763428800619294,

        z(t) = 210.372639670927271]


  [t = 7.3, x(t) = 156.744144910668779, y(t) = 628.414372309472582,

        z(t) = 214.841482779858893]


  [t = 7.4, x(t) = 147.159188054819338, y(t) = 633.492182254123350,

        z(t) = 219.348629691056914]


  [t = 7.5, x(t) = 138.094056648806798, y(t) = 638.015893105380655,

        z(t) = 223.890050245812204]


  [t = 7.6, x(t) = 129.532183516512788, y(t) = 642.005948716919306,

        z(t) = 228.461867766568076]


  [t = 7.7, x(t) = 121.455837603002919, y(t) = 645.483815647616097,

        z(t) = 233.060346749381068]


  [t = 7.8, x(t) = 113.846267518008815, y(t) = 648.471832261671693,

        z(t) = 237.681900220319164]


  [t = 7.9, x(t) = 106.684072930480581, y(t) = 650.992811778617920,

        z(t) = 242.323115290901200]


  [t = 8.0, x(t) = 99.9495046301988452, y(t) = 653.069754819129684,

        z(t) = 246.980740550671498]


  [t = 8.1, x(t) = 93.6226138684905180, y(t) = 654.725704146893235,

        z(t) = 251.651681984616090]


  [t = 8.2, x(t) = 87.6834534834608661, y(t) = 655.983531031732695,

        z(t) = 256.333015484806310]


  [t = 8.3, x(t) = 82.1122877444257426, y(t) = 656.865731572541676,

        z(t) = 261.021980683032382]


  [t = 8.4, x(t) = 76.8896927697057180, y(t) = 657.394336682508765,

        z(t) = 265.715970547785218]


  [t = 8.5, x(t) = 71.9966681247414044, y(t) = 657.590795308706219,

        z(t) = 270.412536566552433]


  [t = 8.6, x(t) = 67.4147599056724402, y(t) = 657.475857007423428,

        z(t) = 275.109383086904017]


  [t = 8.7, x(t) = 63.1261038106340209, y(t) = 657.069540593403985,

        z(t) = 279.804355595962248]


  [t = 8.8, x(t) = 59.1134864627066250, y(t) = 656.391071421150400,

        z(t) = 284.495442116143124]


  [t = 8.9, x(t) = 55.3604016691298782, y(t) = 655.458831790789986,

        z(t) = 289.180766540080184]


  [t = 9.0, x(t) = 51.8510508440606017, y(t) = 654.290371511227362,

        z(t) = 293.858577644712170]


  [t = 9.1, x(t) = 48.5703734048092670, y(t) = 652.902378013005659,

        z(t) = 298.527248582185393]


  [t = 9.2, x(t) = 45.5040568465927677, y(t) = 651.310673738806372,

        z(t) = 303.185269414600668]


  [t = 9.3, x(t) = 42.6385127801171677, y(t) = 649.530249551642896,

        z(t) = 307.831237668240191]


  [t = 9.4, x(t) = 39.9608879821651186, y(t) = 647.575255143111007,

        z(t) = 312.463856874723717]


  [t = 9.5, x(t) = 37.4590453022256895, y(t) = 645.459025799451183,

        z(t) = 317.081928898322928]


  [t = 9.6, x(t) = 35.1215296671879500, y(t) = 643.194124094616654,

        z(t) = 321.684346238195530]


  [t = 9.7, x(t) = 32.9375671213985796, y(t) = 640.792342771204630,

        z(t) = 326.270090107396470]


  [t = 9.8, x(t) = 30.8970297366373501, y(t) = 638.264747160929459,

        z(t) = 330.838223102433403]


  [t = 9.9, x(t) = 28.9904003633449002, y(t) = 635.621716509479711,

        z(t) = 335.387883127175598]


  [t = 10.0, x(t) = 27.2087645292290930, y(t) = 632.872954175775703,

        z(t) = 339.918281294995210]


  [t = 10.1, x(t) = 25.5437688634773004, y(t) = 630.027535824813071,

        z(t) = 344.428695311709702]


  [t = 10.2, x(t) = 23.9875887695550282, y(t) = 627.093946491590258,

        z(t) = 348.918464738854595]


  [t = 10.3, x(t) = 22.5329166478323124, y(t) = 624.080094435228148,

        z(t) = 353.386988916939401]


  [t = 10.4, x(t) = 21.1729200358625000, y(t) = 620.993358722969106,

        z(t) = 357.833721241168234]


  [t = 10.5, x(t) = 19.9012134814395054, y(t) = 617.840621067059373,

        z(t) = 362.258165451501270]


  [t = 10.6, x(t) = 18.7118456079140678, y(t) = 614.628280674413758,

        z(t) = 366.659873717672155]


  [t = 10.7, x(t) = 17.5992605259082922, y(t) = 611.362297632110881,

        z(t) = 371.038441841980500]


  [t = 10.8, x(t) = 16.5582737234475772, y(t) = 608.048219977591997,

        z(t) = 375.393506298960346]


  [t = 10.9, x(t) = 15.5840596895435066, y(t) = 604.691197741936434,

        z(t) = 379.724742568519616]


  [t = 11.0, x(t) = 14.6721183351318203, y(t) = 601.296020447312116,

        z(t) = 384.031861217556411]


  [t = 11.1, x(t) = 13.8182541277570348, y(t) = 597.867140406375142,

        z(t) = 388.314605465868396]


  [t = 11.2, x(t) = 13.0185652772222724, y(t) = 594.408684918439576,

        z(t) = 392.572749804338059]


  [t = 11.3, x(t) = 12.2694158357106673, y(t) = 590.924487289174067,

        z(t) = 396.806096875115599]


  [t = 11.4, x(t) = 11.5674171524732081, y(t) = 587.418107457316182,

        z(t) = 401.014475390210578]


  [t = 11.5, x(t) = 10.9094190304092518, y(t) = 583.892841937697767,

        z(t) = 405.197739031892695]


  [t = 11.6, x(t) = 10.2924876380279482, y(t) = 580.351748313120993,

        z(t) = 409.355764048850972]


  [t = 11.7, x(t) = 9.71388843554550085, y(t) = 576.797664166972026,

        z(t) = 413.488447397481706]


  [t = 11.8, x(t) = 9.17107923126182100, y(t) = 573.233214878079138,

        z(t) = 417.595705890659019]


  [t = 11.9, x(t) = 8.66169377837968923, y(t) = 569.660831787016832,

        z(t) = 421.677474434603425]


  [t = 12.0, x(t) = 8.18352558759921854, y(t) = 566.082770103624511,

        z(t) = 425.733704308776907]


  [t = 12.1, x(t) = 7.73452244392691757, y(t) = 562.501115050994486,

        z(t) = 429.764362505078962]


  [t = 12.2, x(t) = 7.31277529362930690, y(t) = 558.917794181351268,

        z(t) = 433.769430525019288]


  [t = 12.3, x(t) = 6.91650287007108222, y(t) = 555.334594354097021,

        z(t) = 437.748902775831766]


  [t = 12.4, x(t) = 6.54404706002732439, y(t) = 551.753166907423065,

        z(t) = 441.702786032549625]


  [t = 12.5, x(t) = 6.19386601529495272, y(t) = 548.175035321736231,

        z(t) = 445.631098662968383]


  [t = 12.6, x(t) = 5.86452049310677736, y(t) = 544.601610284815365,

        z(t) = 449.533869222077782]


  [t = 12.7, x(t) = 5.55466932070783503, y(t) = 541.034194725323346,

        z(t) = 453.411135953968710]


  [t = 12.8, x(t) = 5.26306483191776930, y(t) = 537.473988920937131,

        z(t) = 457.262946247145009]


  [t = 12.9, x(t) = 4.98854296681376130, y(t) = 533.922101409549554,

        z(t) = 461.089355623636663]


  [t = 13.0, x(t) = 4.73001722376625810, y(t) = 530.379555674458857,

        z(t) = 464.890427101774889]


  [t = 13.1, x(t) = 4.48647580379716082, y(t) = 526.847293352726296,

        z(t) = 468.666230843476284]


  [t = 13.2, x(t) = 4.25697574432115910, y(t) = 523.326180718723322,

        z(t) = 472.416843536955354]


  [t = 13.3, x(t) = 4.04063545303149230, y(t) = 519.817016918931812,

        z(t) = 476.142347628036588]


  [t = 13.4, x(t) = 3.83663271940328609, y(t) = 516.320536193792918,

        z(t) = 479.842831086803470]


  [t = 13.5, x(t) = 3.64420161497367622, y(t) = 512.837411341829238,

        z(t) = 483.518387043196526]


  [t = 13.6, x(t) = 3.46262586578508991, y(t) = 509.368261018163536,

        z(t) = 487.169113116051448]


  [t = 13.7, x(t) = 3.29123610839315228, y(t) = 505.913652771795568,

        z(t) = 490.795111119810997]


  [t = 13.8, x(t) = 3.12940801364136245, y(t) = 502.474105159538169,

        z(t) = 494.396486826820194]


  [t = 13.9, x(t) = 2.97655873072925514, y(t) = 499.050091674013798,

        z(t) = 497.973349595256934]


  [t = 14.0, x(t) = 2.83214229287906826, y(t) = 495.642045811287914,

        z(t) = 501.525811895832930]


  [t = 14.1, x(t) = 2.69564858145347230, y(t) = 492.250362229209656,

        z(t) = 505.053989189336846]


  [t = 14.2, x(t) = 2.56660151893131516, y(t) = 488.875398779363422,

        z(t) = 508.557999701705398]


  [t = 14.3, x(t) = 2.44455534955230780, y(t) = 485.517480599718794,

        z(t) = 512.037964050728760]


  [t = 14.4, x(t) = 2.32909245355232164, y(t) = 482.176902531316045,

        z(t) = 515.494005015131392]


  [t = 14.5, x(t) = 2.21982251952024168, y(t) = 478.853930055531293,

        z(t) = 518.926247424948541]


  [t = 14.6, x(t) = 2.11638043895373062, y(t) = 475.548801634012363,

        z(t) = 522.334817927034010]


  [t = 14.7, x(t) = 2.01842383376014478, y(t) = 472.261731428594374,

        z(t) = 525.719844737645530]


  [t = 14.8, x(t) = 1.92563214995174214, y(t) = 468.992910315433277,

        z(t) = 529.081457534614968]


  [t = 14.9, x(t) = 1.83770536702454600, y(t) = 465.742507327166890,

        z(t) = 532.419787305808200]


  [t = 15.0, x(t) = 1.75436193638558024, y(t) = 462.510671923943789,

        z(t) = 535.734966139670632]

>