Magnetic moment of an electron in the $n^{th}$ orbit of the hydrogen atom is

Question

$\begin {array} {1 1} (a)\;neh/ \pi \: m & \quad (b)\;neh/4 \pi \: m \\ (c)\;meh/ \pi \: n & \quad (d)\;meh/4 \pi \: n \end {array}$