To solve this problem we will apply the concepts related to electric potential and electric potential energy. By definition we know that the electric potential is determined under the function:

= Coulomb's constant
q = Charge
r = Radius
At the same time

The values of variables are the same, then if we replace in a single equation we have this expression,

If we replace the values, we have finally that the charge is,




Therefore the potential energy of the system is
