An electron is lying initially in the $n=4$ excited state. The electron de-excites itself to go to $n=1$ state directly emitting a photon of frequency $v_{41}$. If the same electron first de-excites to $n=3$ state by emitting a photon of frequency $v_{43}$ and then goes from $n=3$ to $n=1$ state by emitting a photon of frequency $v_{31}$, then