Switch S shown in figure has been closed for a long time, and the electric circuit carries a constant current. Take C$1=3$ microFarad, C$2=6$ microFarad, R$1=4000$ ohm and R$2=7000$ ohm. The power delivered to R$2$ is $2\mathrm{.}4$W$.$ a$)$ Find the charges on C$1$ and C$2.$ b$)$Now the switch S is opened. After many miliseconds, by how much has the charge on C$2$ changed? c$)$ Switch S is closed and after a while the new switch S$1$ is opened. Now capacitor is empty. Than S$1$ is closed at time t$=0.$ What is the equation of Q$1($t$)?($Kirchoff$\text{'}$s Rules can be used$)$