Question

The figure below shows a current loop carrying current I. The
loop is made of rectangular and semicircular sections with
dimensions as shown. The loop lies in the xy-plane.
An external magnetic field is applied B = Bx i + Bz k.
Determine the torque (if any) around the axis labeled AB. If
there is torque, in which direction would the loop tend to
rotate?
Deduce (i.e. without full solution) the answer if the axis of
rotation is the horizontal segment of the loop.