Dielectric Breakdown Occurs in the Air at an Electric Field

Dielectric breakdown occurs in the air at an electric field strength of E_max = 3.0  10⁶ V/m.If the maximum potential at the surface of a spherical conductor is 5.0  10⁶ V,then calculate the radius of the sphere.

A) 0.60 m
B) 1.3 m
C) 1.7 m
D) 0.77 m
E) 15 m