In a hydrogen atom, the electron and proton are bound at a distance of about $0.53 \dot{A}$: What is the minimum work required to free the electron, given that its kinetic energy in the orbit is half the magnitude of potential energy obtained ?

Question

$\begin{array}{1 1} -27.2\;ev \\0.7\;ev \\ 0.4\;ev \\ 13.6\;ev\end{array} $