function ydot=myfun(t,y)
global a b c d ;
ydot(1)=a*y(1)*y(3)/(b+y(3));%biomass
ydot(2)=c/d*a*y(1)*y(3)/(b+y(3));%product
ydot(3)=e*f-1/c*a*y(1)*y(3)/(b+y(3))-y(1)*e/c-y(3)*e;%substrate

ydot=ydot';

