Determine the electrostatic potential energy of a system consisting of two charges $7 \mu C$ and $–2\;\mu C$ (and with no external field) placed at $(–9 cm, 0, 0)$ and $(9 cm, 0, 0)$ respectively.

Question

$\begin{array}{1 1} 0.8\;J \\0.7\;J \\ 0.4\;J \\ 0.9\;J\end{array}$