% Created by Nick Fidalgo, Chris Gatesman, Phillip Less, Brett Peters, Samantha Sandwick, and Alex Shetler
function dydt = hill_m4(t,s,K_m,K_5,om,sig,gam,xi,phi,nu,mu,A_0,a)
%ODE45
B = s(1);
D = s(2);
F = s(3);
E = s(4);
B_ss = 1.000188;
B_0 = 174;
E_0 = 45;
F_0 = 1;
A = A_0*exp(-a*t);
dydt = zeros(3,1);
dydt(1) = -K_m*(A*A_0).^(om)/(sig*(K_5^(om) + (A*A_0).^om))*B + B*(nu*(1-(B/B_ss))-xi)/(sig); 
dydt(2) = K_m*(A*A_0).^(om)/(sig*(K_5^(om) + (A*A_0).^om))*B - D;
dydt(3) = (gam*D)/F_0 + (xi*B*gam)/(sig*F_0) - (mu*F*F_0)/(sig*B_ss*B_0);
dydt(4) = (mu*F*F_0)/(sig*B_ss*B_0)-(phi*E*E_0)/(sig*B_ss*B_0);

end