Using the value of K in Problem 8, compute the gain and phase margins when Td = 0.2.

a. G.M. = 14 dB, P.M. = 27

b. G.M. = 20 dB, P.M. = 64.9

c. G.M. = dB, P.M. = 60

d. Closed-loop system is unstable

For Problems 8 and 9, consider the block diagram in Figure 9.69 where G(s) 9 (s+1)(s+3s+ 9)' and the controller is the proportional-plus-derivative (PD) controller Ge(s) = K(1+Tas).