[QUE/EM-07013] --- EM-PROBLEM --- Torque on current loopin magnetic field

A circular coil is formed from a  wire of length $L$ with $n$ turns. The coil carries a current $I$ and is placed in an external uniform magnetic field  $B$. Show that  maximum torque developed is  $\displaystyle\frac{IBL^2}{4n\pi}$.