A He^+ ion is in its first excited state. Its ionization energy is?

Correct option is B. 13.60eV
Energy levels in Hydrogen like atom is given by
E = -13.6(z²/n²) eV
As He+ is in 1st excited state ∴ z=2, n=2
E = -13.6 eV
As total energy of He+ in 1st excited state is -13.6 eV, ionization energy should be +13.6eV.