Find the maximum frequency of x- rays produced by $30\; kv$ electrons. Given, $h= 6.63 \times 10^{-34}\;Js$

Question

$\begin{array}{1 1} 7.24 \times 10^{18}\;Hz \\ 72.4 \times 10^{18}\;Hz \\ 0.724 \times 10^{18}\;Hz \\ 724 \times 10^{18}\;Hz \end{array}$