Which formula gives the energy stored in a charged capacitor?

If the charge on the capacitor is increased by $3 \ C$,the energy stored in it increases by $44 \%$. The original charge on the capacitor is (in $C$)

If the charge on a body is increased by $2 \ C$,the energy stored in it increases by $21 \%$. The original charge on the body in coulomb is:

If $E$ is the electric field intensity of an electrostatic field,then the electrostatic energy density is proportional to

The energy stored in the capacitor is

$A$ parallel plate capacitor is charged by a battery until the potential difference between the plates equals the electromotive force of the battery. What is the ratio of the energy stored in the capacitor to the work done by the battery?