The Energy Change for an Electronic Transition in a One-Electron $\infty$

The energy change for an electronic transition in a one-electron atom or ion (H,He⁺,Li²⁺,etc.) from n_initial to n_final is given by ,where Z is the atomic number. How much energy is required to ionize a ground-state He⁺ ion (n_final = $\infty$ ) ?

A) 2.18 $\times$ 10^-18 J
B) 4.36 $\times$ 10^-18 J
C) 8.72 $\times$ 10^-18 J
D) 1.09 $\times$ 10^-18 J
E) 5.45 $\times$ 10^-19 J