a$)$ Consider a single$-$loop feedback control system with,

$\backslash [$

G$($s$)$ H$($s$)=\backslash$frac$\{1\}\{$s$($s$-1)($s$+4)\}$

$\backslash ]$

Using Nyquist Plot analyze the stability of the system, please include Nyquist contours to make your decision.

b$)$ Figure $8($b$)$ shows a unity feedback system. Sketch the Nyquist diagram for the system. It looks the open loop system stability is ok as no poles is in the right$-$hand s$-$plan. Determine the closed loop system stability using the Nyquist criterion.