A point charge q is placed inside a conducting spherical shell of inner radius 2R and outer radius 3R at a distance of R from the center of the shell. Find the electric potential at the center of the shell. 

• A

  $\frac{1}{4{\mathrm{\pi \epsilon }}_0}\frac{\mathrm{q}}{2\mathrm{R}}$

• B

  $\frac{1}{4{\mathrm{\pi \epsilon }}_0}\frac{4\mathrm{q}}{3\mathrm{R}}$

• C

  $\frac{1}{4{\mathrm{\pi \epsilon }}_0}\frac{5\mathrm{q}}{6\mathrm{R}}$

• D

  $\frac{1}{4{\mathrm{\pi \epsilon }}_0}\frac{2\mathrm{q}}{3\mathrm{R}}$