For the closed loop system shown in Figure Q2.1:
(a)Determine to what value the gain K should be changed to make this closed-loop system stable if, for K=a+1, the gain margin of the system is negative and equal to -20dB, where parameter a represents the last digit of your student registration number. a= 0
Figure Q2.1

Plant R(S) E(S) U(S) Y(S) + K. G(s)