Find the charge in steady state of the capacitor. (in $nC$)

In the transient circuit shown,the time constant of the circuit is:

$A$ $4 \mu F$ capacitor and a resistance of $2.5 \, M\Omega$ are in series with a $12 \, V$ battery. Find the time after which the potential difference across the capacitor is $3$ times the potential difference across the resistor. (Given $\ln(2) = 0.693$)

In an $R-C$ charging circuit,the dashed line represents the graph of $\ln I$ versus $t$. If the resistance of the circuit is doubled,which of the following solid lines represents the correct graph of $\ln I$ versus $t$?

After the switch shown in Figure $A$ is closed,there is a current $i$ through the resistance $R$. Figure $B$ indicates current variation curves $a, b, c,$ and $d$ for four sets of values of $R$ and capacitance $C$:
$(i)$ $R_0$ and $C_0$
$(ii)$ $2R_0$ and $C_0$
$(iii)$ $R_0$ and $2C_0$
$(iv)$ $2R_0$ and $2C_0$
Which set goes with which curve?

During charging and discharging of a capacitor: