21. Figure 5 shows a block diagram of a system using SIMULINK. It can be shown that the corresponding differential equation can be expressed as y" + ay' + by = f(t). Find the values of "a" and "b". Explain your answer step-by- step indicating each signal before and after each Gain, Integrator, and Add block. (10 points) Step f(t)= = 5 + Add 2 Gain1 3 Gain3 Integrator 1.5 Gain2 3 7 Gain Integrator1 y Scope