function output = pos_reg(tspan, IC, k_prod, k_deg, kd)

A = IC(1); % Initial state of A
B = IC(2); % Initial state of B 

dAdt = k_prod - k_deg*A;  %Diff EQ for A
dBdt = A/(kd + A) - k_deg*B; %Diff EQ for B (A activates B)

%Make sure your output is in columns
output = [dAdt; dBdt]; 
end 