A hydrogen atom in the ground state is hit by a particle exciting the electron to 4s orbital.The electron then drops to 2s orbital.What is the frequency of radiation emitted and absorbed in the process?

Question

$\begin{array}{1 1}(a)\;6.15\times 10^{15}Hz&(b)\;7\times 10^{14}Hz\\(c)\;3\times 10^{13}Hz&(d)\;3.5\times 10^{12}Hz\end{array}$