The dipole moment of a short bar magnet is 1.25 A−m². The magnetic field on its axis at a distance of 0.5 metre from the centre of the magnet is

A. 1.0×10⁻⁴ Newton/amp-meter
B. 4×10⁻² Newton/amp-meter
C. 2×10⁻⁶ Newton/amp-meter
D. 6.64×10⁻⁸ Newton/amp-meter