How much time does it take for the current to decay to half of its initial value in the following charging circuit?

In the circuit shown in the diagram,the capacitances of the capacitors $C_1$,$C_2$,and $C_3$ are $4\ \mu F$,$6\ \mu F$,and $12\ \mu F$ respectively. The switch $S$ remains closed for a long time. When the switch $S$ is opened,which of the following statements will be correct about the current flowing through the battery $B$?

Two identical capacitors $A$ and $B$ are charged to the same potential $V$ and are connected in two circuits at $t = 0,$ as shown in the figure. The charge on the capacitors at time $t = CR$ are respectively:

In the following circuit,the switch $S$ is closed at $t = 0.$ The charge on the capacitor $C_1$ as a function of time will be given by $\left( {{C_{eq}} = \frac{{{C_1}{C_2}}}{{{C_1} + {C_2}}}} \right).$

Find the charge on the capacitor $C = 2 \, \mu F$ in the given circuit in $\mu C$.

$A$ capacitor is a perfect insulator for