Two equal charges \[q\] are placed at a distance of \[2a\] and a third charge \[-2q\] is placed at the midpoint. The potential energy of the system is [MP PMT 1997]

• A.                    \[\frac{{{q}^{2}}}{8\pi {{\varepsilon }_{0}}a}\]
• B.                                      \[\frac{6{{q}^{2}}}{8\pi {{\varepsilon }_{0}}a}\]
• C.                    \[-\frac{7{{q}^{2}}}{8\pi {{\varepsilon }_{0}}a}\]
• D.                                      \[\frac{9{{q}^{2}}}{8\pi {{\varepsilon }_{0}}a}\]