A current carrying circular loop of magnetic moment $\vec{M}$ is suspended in a vertical plane in an external magnetic field $\vec{B}$ such that its plane is normal to $\vec{B}$. The work done in rotating this loop by $45^\circ$ about an axis perpendicular to $\vec{B}$ is closest to : (A) $-0.3 \text{ MB}$ (B) $0.3 \text{ MB}$ (C) $-1.7 \text{ MB}$ (D) $1.7 \text{ MB}$