An uncharged metallic sphere A of radius R is concentrically placed inside another sphere. Then metallic spherical shell of radius 2R carrying a charge Q. Now the sphere A is earthed. If P be a point at a radial distance 1.5 R from the centre of the spheres, then potential at P is

• A

  $\raisebox{1ex}{$\mathrm{Q}$}\!\left/ \!\raisebox{-1ex}{$36$}\right. {\mathrm{\pi \epsilon }}_{\mathrm{o}}\mathrm{R}$

• B

  $\raisebox{1ex}{$\mathrm{Q}$}\!\left/ \!\raisebox{-1ex}{$24$}\right. {\mathrm{\pi \epsilon }}_{\mathrm{o}}\mathrm{R}$

• C

  $\raisebox{1ex}{$\mathrm{Q}$}\!\left/ \!\raisebox{-1ex}{$16$}\right. {\mathrm{\pi \epsilon }}_{\mathrm{o}}\mathrm{R}$

• D

  $\raisebox{1ex}{$\mathrm{Q}$}\!\left/ \!\raisebox{-1ex}{$12$}\right. {\mathrm{\pi \epsilon }}_{\mathrm{o}}\mathrm{R}$