Electric potential energy or electric field potential refers to the amount of potential energy per unit of charge and it's measured in joules/coulomb. The electric potential energy of q in the potential of Q1 can be obtained with the potential energy formula. Here qN (8.8541878176e-12 F/m) is the charge, ε0 is permittivity and rN is the separation between the two point charges. Substitute the given values into the formula to find the electric potential energy of system of charges.
Make use of the above potential energy formula to find the electric potential energy of system of charges ie., the system connected with 'n' charge points (q1, q2,....... qn).