A closed-loop system with unity feedback has a loop transfer function
$$
G_c(s) G(s)=\frac{K(s+20)}{s^2} .
$$
(a) Determine the gain $K$ so that the phase margin is $45^{\circ}$. (b) For the gain $K$ selected in part (a), determine the gain margin. (c) Predict the bandwidth of the closed-loop system.