A bar magnet having a magnetic moment of $2 \times 10^{4} \mathrm{JT}^{-1}$ is free to rotate in a horizontal plane. A horizontal magnetic field $\mathrm{B}=6 \times 10^{-4}$ Tesla exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction $60^{\circ}$ from the field is
(a) $0.6 \mathrm{~J}$
(b) $12 \mathrm{~J}$
(c) $6 \mathrm{~J}$
(d) $2 \mathrm{~J}$