A bar magnet of magnetic moment $4 A-m^2$ is free to rotate about a vertical axis through its centre. The magnet is released from rest from east-west position. Kinetic energy of the magnet in the north- south position will be $(H = 25 \mu T)$

Question

$\begin {array} {1 1} (a)\;10^{-2}J & \quad (b)\;10^{-4}J \\ (c)\;10^{-6}J & \quad (d)\;0 \: J \end {array}$