Determine the voltage $v_L$ across the inductor in Figure P4.38 for all time. Assume DC steady-state conditions for $t<0$. Also assume: $V_S=15 \mathrm{~V}, L=200 \mathrm{mH}, R_S=1 \Omega$, and $R_1=20 \mathrm{k} \Omega$.
(FIGURE CAN'T COPY)
Figure P4.38