The potential energy of a pair of point charges is given by:
[tex]U=k\frac{q_1q_2}{r}[/tex]In this case we have that the distance between the charges is 0.93 m and the charges are 1 nC and 2 nC; plugging these values we have:
[tex]\begin{gathered} U=(9\times10^9)\frac{(1\times10^{-9})(2\times10^{-9})}{(0.93)} \\ U=19.35\times10^{-9} \end{gathered}[/tex]Therefore, the potential energy is 19.35 nJ
