For the block diagram of a closed$-$loop system on the Figure,

Derive a closed$-$loop transfer function for disturbance changes, $Y\frac{s}{D}(s).$

For the following transfer functions, what values of $Kc$ will result in a stable closed$-$loop system?

$G_m=\frac{1}{s+1}$

$G_2(s)=\frac{5}{2s+1}$

$G_1(s)=6$

$G_3(s)=\frac{1}{s-1}$