Do it by calculation

In biochemical reactions, the substrate is the substance on which an enzyme acts. The dynamic response of a stirred-tank bioreactor in Tubli water treatment plant can be represented by the transfer function: CF(s)C(s)=3s+15 Where C(s) is the exit substrate concentration, mol/L and CF is the feed substrate concentration, mol/L. Derive an expression for c(t) if cA(t) is a rectangular pulse with the following characteristics: CF(t)=3,5,3,t