An infinitesimally small bar magnet of dipole moment \[\vec{M}\] is pointing and moving with the speed v in the \[\hat{x}\]- direction. A small closed circular conducting loop of radius a and negligible self- inductance lies in the y-z plane with its center at x = 0, and its axis coinciding with the x-axis. Find the force opposing the motion of the magnet, if the resistance of the loop is R. Assume that the distance x of the magnet from the center of the loop is much greater than a.

• A. \[\frac{21}{4}\frac{\mu _{0}^{2}{{M}^{2}}{{a}^{4}}v}{R{{x}^{8}}}\]     
• B. \[\frac{16}{3}\frac{{{\mu }_{0}}{{M}^{2}}{{a}^{2}}{{v}^{2}}}{R{{x}^{3}}}\]
• C. \[\frac{3}{23}\frac{{{\mu }_{0}}Ma{{v}^{2}}}{R{{x}^{3}}}\]          
• D. None of these