Four charges \[{{q}_{1}}=2\times {{10}^{-8}}C,\] \[{{q}_{2}}=-2\times {{10}^{-8}}C,\]\[{{q}_{3}}=-3\times {{10}^{-8}}C\], \[{{q}_{3}}=6\times {{10}^{-8}}C\]are placed at four corners of a square of side \[\sqrt{2}\] m. What is hollow spheres of radii r and R (R > r) such that the common center of the square?

• A. 270 V
• B. 300 V
• C. Zero     
• D. 100 V