[QUE/EM-01004] --- EM-PROBLEM

A gold nucleus contains a positive charge equal to that of 79 protons. An $\alpha$ particle, $Z=2$, has kinetic energy $K$ at points far away from the nucleus and is traveling directly towards the  charge, the particle just touches the surface of the charge and is reversed in direction. relate $K$ to the radius of the gold nucleus. Find the numerical value of kinetic energy in MeV is the radius $R$ is given to be $5 \times10^{-15}$ m.

[ 1 MeV = $10^6$ eV and 1 eV = $1.6\times10^{-16}$]