Suppose that a simple proportional controller is utilized, that is, Gc1s2 = K. Using the root locus method, determine the maximum controller gain K for closed-loop stability.

a. K = 0.50

b. K = 1.49

c. K = 4.49

d. Unstable for K 7 0

G(s) = 7500 (s+1)(s+10) (s + 50)*