Hello, I am trying to write a program on matlab using ode45 to solve the following equations: S'=-bSZ-sS Z'=bSZ+gR-aSZ R'=sS+aSZ-gR These are all derivatives with respect to t, differential equations. a, b, a and g are all constants. I realise I need to have two m files, one which defines the functions, and one which calls that and uses ode45. The code for my first m file is: function Yout = program1(S,Z,R); global beta gamma alpha sigma; % set the parmeter values tend = 10; S0 = 500; I0 = 1; b=0.0095; g=0.0001; a= 0.005; s=0.0001; Sdot=(-b)*S*Z-(gg*S); Zdot=(b*S*Z)+(g*R)-(a*S*Z); Rdot=(s*S)+(a*S*Z)-(g*R); udot = [Sdot; Zdot; Rdot]; I'm not sure if that is suitable, and I also need help writing the second m file. I need to plot Z and R on the same plot, vs t. I am really stuck, I have been working for hours, looking at examples, trying different combinations. MATLAB is most definitely not my strong point. Thanks for the help!