For the following nonhomogeneous input-output differential equations (InputOutput models), find their respective system responses:

(a)

\[\begin{aligned}\ddot{y}+4 \dot{y}+3 y & =u(t) \\\text { where } y(0) & =1, \dot{y}(0)=0 \text { and } u(t)=2\end{aligned}\]

(b)
\[\begin{aligned}
\ddot{y}+5 \dot{y}+4 y & =u(t) \\\text { where } y(0) & =\alpha, \dot{y}(0)=\beta \text { and } u(t)=3 \end{aligned}\]

(c)
\[\begin{aligned}\ddot{y}+5 \dot{y}+4 y & =u(t) \\\text { where } y(0) & =0, \quad \dot{y}(0)=0 \text { and } u(t)=2 e^{-2 t}\end{aligned}\]