An excited He⁺ ion emits two photons in succession, with wavelengths 108.5 nm and 30.4 nm, in making a transition to ground state. The quantum number n, corresponding to its initial excited is (for photon of wavelength λ energy E=1240 eV/λ (in nm)
A. n=5
B. n=4
C. n=7
D. n=6
