function [ dDEdt ] = LuciaIRamirezDE(t,DE)
% this function was given by instructor
global s V K p t 

dDEdt = zeros(size(DE));

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

dsdt = -(V*s)/(K+s); 
dpdt = (V*s)/(K+s);

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