$(30$ p$)4-$A unity feedback system is given as below:

For this system,

a$)$ If $C(s)=K,$ find the range of $K$ values to make this system underdamped.

b$)$ If $C(s)=25,$ draw the step response by calculating peak time, maximum overshoot and steady state error.

c$)$ If $C(s)=\frac{1}{s},$ calculate the steady state error of the response when the reference signal $r(t)=t.$