Electrostatics

Two point charges '\(q 1\)' and '\(q 2\)' are separated by a distance '\(d\)'. What is the increase in potential energy of the system when '\(q 2\)' is moved towards '\(q 1\)' by a distance '\(\mathrm{x}\)' ?
\((x < d)(\frac{1}{4 \pi \varepsilon_0}=K\), constant)