Determine the equivalent impedance seen by the voltage source $v_S$ in Eigure P3.47 when:
$$
\begin{aligned}
v_3(t) & =10 \cos (4,000 \mathrm{r}+600) \mathrm{V} \\
R_1 & =800 \Omega \quad R_2=500 \Omega \\
L & =200 \mathrm{mH} \quad C=70 \mathrm{nF}
\end{aligned}
$$
Figure P3.47