$9\mathrm{.}9.$ The switch in the circuit has been closed for a long time. The switch opens at t$=0$sec$.$ Find v$\_(0)($t$)$

for t$>0$sec$.$ What is the energy stored in L at t$=160$ microsecond?

D$\mathrm{.}10.$ For tS$\_(1)$ was ON and S$\_(2)$ was OFF. At t$=0$sec$.$S$\_(1)$ is turned OFF and S$\_(2)$ is turned ON $.$

Find v$\_($R$)($t$)$ at t$=30$ millisecond.

D$\mathrm{.}11.$ The energy on the inductor is initially t$=0$

second. Find the current on inductor L at t$=2\mathrm{.}5$ microsecond. The inductor L is $1$ mH $.$

D$\mathrm{.}12.$ Find the value of R$,$ if the energized inductor L spends $20\%$ of its energy in $10$ msec after the

switch is turned ON$.$