Potential Energy of a Current Loop: a Rigid Circular Loop

Potential energy of a current loop: A rigid circular loop has a radius of 0.20 m and is in the xy-plane. A clockwise current I is carried by the loop, as shown. The magnitude of the magnetic moment of the loop is 0.75 A ∙ m². A uniform external magnetic field, B = 0.20 T in the positive x-direction, is present. An external torque changes the orientation of the loop from one of lowest potential energy to one of highest potential energy. The work done by this external torque is closest to

A) 0.20 J
B) 0.30 J
C) 0.40 J
D) 0.50 J
E) 0.60 J