The wavelength of the radiations emitted,when in a hydrogen atom electron falls from infinity to stationary state is ($R_H=1.097\times 10^7m^{-1})$

Question

$\begin{array}{1 1}(a)\;9.1\times 10^{-8}nm\\(b)\;192nm\\(c)\;406nm\\(d)\;91nm\end{array}$