What is the effective capacitance between $A$ and $B$ in the following figure in $\mu F$?

Two parallel plate air capacitors are connected in parallel. Each capacitor has plate area $A/2$ and separation between the plates is $d$ and $2d$ respectively. The equivalent capacity of the combination is $(\epsilon_0 = \text{absolute permittivity of free space})$

In the circuit,two capacitors $C_1$ and $C_2$ are connected as shown in the figure. The potential at point $A$ is $V_1$ and at point $B$ is $V_2$. What is the potential at point $D$?

Three capacitors $C_1$,$C_2$,and $C_3$ are connected in parallel,and their equivalent capacitance is $12$ units. Given $C_1 \cdot C_2 \cdot C_3 = 48$ units. When $C_1$ and $C_2$ are connected in parallel,their equivalent capacitance is $6$ units. Find the individual capacitances $C_1, C_2, C_3$.

An infinite number of capacitors with capacitances $C, 4C, 16C, ... \infty$ are connected in series. What is the equivalent capacitance of the combination in terms of $C$?

In the given figure,the equivalent capacitance between points $A$ and $B$ is (in $C$)