A gaseous mixture contains hydrogen atoms in the 4^th excited state, `He^+` ions in 3^rd excited state and `Li^(2+)` in 2^nd excited state. The number of spectral lines obtained in the emission spectrum of this sample when all these atoms/ions return to the ground state is

A gaseous mixture contains hydrogen atoms in the 4th excited state, `He^+` ions in 3rd excited state and `Li^(2+)` in 2nd excited state. The number of spectral lines obtained in the emission spectrum of this sample when all these atoms/ions return to the ground state is

A gaseous mixture contains hydrogen atoms in the 4^th excited state, `He^+` ions in 3^rd excited state and `Li^(2+)` in 2^nd excited state. The number of spectral lines obtained in the emission spectrum of this sample when all these atoms/ions return to the ground state is