At the nuclear plant, a uranium$-235$ nucleus captures a neutron to form an unstable uranium$-236$ nucleus undergoing nuclear fission. Sometimes the two fission products are a barium nucleus $($charge $56$e $)$ and a krypton nucleus $($charge $36$e $).$ Assume that immediately after the split these nuclei are positive point charges separated by the sum of the radii of the barium and krypton nuclei$).$ Calculate the potential energy of this two-charge system in electron volts.