$4\mathrm{.}89($a$)$ Obtain the equations of motion of the system shown in Figure P$4\mathrm{.}89.$ The masses are $m_1=30kg$ and $m_2=70kg.$ The spring constants are $k_1=3{10}^4\frac{N}{m}$ and $k_2=6{10}^4\frac{N}{m}.($b$)$ Obtain the transfer functions $x_1\frac{s}{F}(s)$ and $x_2\frac{s}{F}(s).($c$)$ Obtain a plot of the unit$-$step response of $x_1$ for zero initial conditions. PLEASE HELP WITH PART C