$(20$ points$)$ Consider the circuit below. Assume the switch has been in its initial position for a long time, and it switches position as indicated at $t=0.$

$$

Think about voltage across parallel components. Can you modify the circuit to make it easier to find $v(t)?$

b$.$ How much energy is stored in $C_1$ at $t=2ms.($Answer: $143\mathrm{.}86$ nJ $)$

c$.$ How much energy is stored in $C_2$ at $t=2ms.($Answer: $215\mathrm{.}78$ nJ $)$