$2\frac{Y(s)}{R(s)}=T(s)=\frac{K_2}{s^2+(K_1+K_2{K}_3+K_1{K}_2)s+K_1{K}_2{K}_3}$

b$.\frac{Y(s)}{R(s)}=T(s)=\frac{K_1{K}_2}{s^2+(K_1+K_2{K}_3+K_1{K}_2)s+K_1{K}_2}$

c $\frac{Y(s)}{R(s)}=T(s)=\frac{K_1{K}_2}{s^2+(K_1+K_2{K}_3+K_1{K}_2)s+K_1{K}_2{K}_3}$

d$.\frac{Y(s)}{R(s)}=T(s)=\frac{K_1{K}_2}{s^2+(K_1+K_2+K_1{K}_2)s+K_1{K}_2{K}_3}$

$7-$ Consider the closed$-$loop transfer function

$T(s)=\frac{A_1+k{A}_2}{A_3+k{A}_4}$

where $A1,A2$ and A $3$ are constants then, $S^{T}k=$

$S_C{S}_2=\frac{k(A_1+k{A}_2)}{(A_3+k{A}_4)}$

$s_k^{\text{'}}=\frac{k(A_2{A}_3-A_1{A}_4)}{(A_3+k{A}_4)(A_1+k{A}_2)}$

$d-S_k^T=\frac{k(A_3+k{A}_4)}{(A_1+k{A}_2)}$