please see the image......

The couple (due to force acting on the two parallel sides of the coil which are perpendicular to the magnetic field; for other two force is zero)
= Couple per unit twist X ((/180) X0.5))
will balance out the magnetic torque
= X B = BSin
Where = 89.5 degree

The coil will deflect only when one of the side (Perpendicular to the magnetic field) is fixed, else the coil will simply rotate. The torque exerted due to the magnetic field can be calculated from,
[\mu] X B = [\mu] BSin [\theta]
Now, the other torque is due to the torsion induced because on side is fixed. Hence the torsion is resisted by the internal stress generated, whose magnitude here can be easily calculated as the couple per unit suspension is given. Find total couple due to suspension (Stress) by,
Couple per unit twist X (( [\pi] /180) X0.5))
These two must be equal at 0.5 degree, because the suspension is now in equilibrium.