E7.12 A unity feedback system has a loop transfer function

L(s) = KG(s) = K(s+1) s(s+68+18) (a) Sketch the root locus for K > 0. (b) Find the roots when K = 10 and 20. (c) Compute the rise time, per- cent overshoot, and settling time (with a 2% criterion) of the system for a unit step input when K = 10 and 20.