The nuclear charge (Ze) is nonuniformly distributed within a nucleus of radius R. The charge density p(r) (change per unit volume) is dependent only on the radial distance r from the center of the nucleus as shown in figure, the electric field is only along the radial direction.
The electric field at r = R

Options

A. independent of a
B. directly proportional to a
C. directly proportional to `a^2`
D. inversely proportionaly to a