Design of a pd controller

Question

Assignment:

The block diagram of a control system is given below. The inner loop is positive feedback, i.e. Ks>0,and hence the system is unstable. Adding a P-D controller on the forward channel and a unity negative feedback, one can stabilize the system. Find:

1. The conditions of K_c  and T_c to stabilize the system.
2. The value of K_c and T_c  to let M_p=163% and t_s=0.8, when K_s=0.8 .