Potential Energy in a Three-Charge System

A system of three point charges is arranged in the xy-plane: $q_1 = 2q$ is at the origin, $q_2 = -q$ is at $(d,0)$, and $q_3 = 3q$ is at $(0,d)$. What fraction of the system’s total electric potential energy is contributed by the interaction between charges $q_1$ and $q_3$?