The electrostatic energy of Z protons uniformly distributed...

The electrostatic energy of Z protons uniformly distributed throughout a spherical nucleus of radius R is given by $E = \dfrac{3}{5}\dfrac{Z\left(Z - 1\right){e}^{2}}{4\pi{ε}_{0}R}$ The measured masses of the neutron, $H 11 , O 815$ are 1.008665 u, 1.007825 u, 15.000109 u and 15.003065 u respectively. Given that the radii of both the $N 715 and O 815$ nuclei are same, 1u = 931.5 Me V/ ${c}^{2}$ (c is the speed of light)$and \dfrac{{e}^{2}}{\left(4\pi{ϵ}_{0}\right)} = 1.44MeVfm .$ Assuming that the difference between the binding energies of $N 715 and O 815$ is purely due to the electrostatic energy, the radius of either of the nuclei is $\left(1fm = {10}^{- 15}m\right)$