A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. the energy required to rotate it by $60^o$ is $W$, Now the torque required to keep the magnet in this new position is.

A bar magnet for dipole moment $10^{4}J{T}^{-1}$ is free to rotate around a horizontal plane. A horizontal magnetic field $4\times 10^{-5}T$ exists on the space. Find the work done in rotating the magnet slowly from a direction parallel to the field to a direction $60^0$ from the field.