Two figures are shown as Fig. $A$ and Fig. $B$. The time constant of Fig. $A$ is $\tau_A$ and time constant of Fig. $B$ is $\tau_B$. Then

Three parallel plate capacitors of capacitances $4 \mu \mathrm{~F}$, $6 \mu \mathrm{~F}$ and $12 \mu \mathrm{~F}$ are first connected in series and then in parallel. The ratio of the effective capacitances in the two cases is

Two condensers $C_1$ and $C_2$ in a circuit are joined as shown in the figure. The potential of point $A$ is $V_1$ and that of point $B$ is $V_2$. The potential at point $D$ will be

Four condensers each of capacitance $8 \mu \mathrm{~F}$ are joined as shown in the figure. The equivalent capacitance between the points $A$ and $B$ will be