4. Consider a mass of weight m kg, attached to an ideal spring with spring constant 9N/m and with internal friction 0.5kg/s, subject to a periodic forcing of F(t) = 5 sin 2t. (a) Write down the ODE describing the displacement y(t) of the spring from its rest length, and solve for its steady-state response, assuming y(0) = y'(0) = 1. (b) Find the amplitude R of the steady-state response. Then, by calculating Im (or using a similarly mathematically-grounded procedure), determine the value of the mass that produces the largest response. Interpret your answer, by relating it to concepts we learned in class