An electron of energy $2000\;eV$ describes a path in magnetic field of flux density $0.2\;T$ What is the radius of this path ?

Question

$\begin{array}{1 1} 7.5 \times 10^4 \;m \\ 7.5 \times 10^{-4}\;m \\ 7.5 \times 10^{5}\;m \\ 7.5 \times 10^{-5}\;m \end{array} $