The electric potential at a point $\mathrm{A}$ due to system given below is (Where $\mathrm{k} = \frac{1}{4{\mathrm{\pi \epsilon }}_0}$)

For the isolated charged conductor shown in the figure, if the electric field at point $A$ and $B$ is $E_A$ and $E_B$ respectively, then

A positive charge $q$ is carried slowly from a point, $x$ to point $y$ in an electric field of point charge $+Q$. The work done by external force is

In the following circuit the equivalent capacitance between points $A$ and $B$ is
(capacitance of each capacitor is $2\mu \mathrm{F}$)

Equivalent capacitance between $A$ and $B$ is