function [ dedt ] = inclass(t,e)
global k2 k4 K M e0 f0 

dedt=zeros(size(e))

s= e(1); 
p= e(2);

dsdt  = ((-k2*e0*s*p)/(K+s))+((k4*f0*s*p)/(M+p));
dpdt  = ((k2*e0*s*p)/(K+s))-((k4*f0*s*p)/(M+p));

dedt(1) = dsdt;
dedt(2) = dpdt;
end