Each corner of a cube of side l has a negative charge, -q. The electrostatic potential energy of a charge q at the center of the cube is

• A. \[-\frac{4{{q}^{2}}}{\sqrt{2}\pi {{\varepsilon }_{0}}l}\]
• B.        \[\frac{\sqrt{3}{{q}^{2}}}{4\pi {{\varepsilon }_{0}}l}\]
• C. \[\frac{4{{q}^{2}}}{\sqrt{2}\pi {{\varepsilon }_{0}}l}\]
• D.        \[-\frac{4{{q}^{2}}}{\sqrt{3}\pi {{\varepsilon }_{0}}l}\]