Identical charges each of – q are placed at each corners of cube of side 'b'. Then electrostatic potential energy of charge  +q which is placed at the centre of the cube will be

• A

  $\frac{-4\sqrt{2}{\text{ q}}^{\text{2}}}{\mathrm{\pi } {\mathrm{\epsilon }}_0\mathrm{b}}$

• B

  $\frac{-8\sqrt{2}{\text{ q}}^{\text{2}}}{\mathrm{\pi } {\mathrm{\epsilon }}_0\mathrm{b}}$

• C

  $\frac{-4{\text{q}}^{\text{2}}}{\sqrt{3}\mathrm{\pi } {\mathrm{\epsilon }}_0\mathrm{b}}$

• D

  $\frac{8\sqrt{2}{\text{q}}^{\text{2}}}{4\mathrm{\pi } {\mathrm{\epsilon }}_0\mathrm{b}}$