Q$3)$ Practice Problem $13\mathrm{.}3$

For the circuit in Fig. $13\mathrm{.}18,$ determine the coupling coefficient and the energy stored in the coupled inductors at $t=1\mathrm{.}5s.$

Q$4)$ Practice Problem $13\mathrm{.}4$

Find the input impedance of the circuit in Fig. $13\mathrm{.}25$ and the current from the voltage source.

Figure $13\mathrm{.}25$