Change in Electric Potential Energy

Two point charges, $q_1 = +3.0\,\mu\mathrm{C}$ and $q_2 = -2.0\,\mu\mathrm{C}$, are moved from an initial separation of $0.50\,\text{m}$ to a final separation of $0.25\,\text{m}$. What is the change in the electric potential energy of the system?