In $\mathrm{Li}^{++}$, electron in first Bohr orbit is excited to a level by a radiation of wavelength $\lambda$. When the ion gets deexcited to the ground state in all possible ways (including intermediate emissions), a total of six spectral lines are observed. What is the value of $\lambda$ ? (Given: $\mathrm{h}=6.63 \times 10^{-34} \mathrm{Js} ; \mathrm{c}=3 \times 10^8 \mathrm{~ms}^{-1}$ )