Due to the presence of the current I, at the origin

Question

( A ) The forces on AD and BC are zero
( B ) The magnitude of the net force on the loop is given by $\frac{\mu_o I}{4 \pi} [ 2 (b-a) + \frac{\pi}{3} (a+b) ]$
( C ) The forces on AB and DC are zero
( D ) The magnitude of the net force on the loop is given by $\frac{\mu_o I}{4 \pi} \begin{bmatrix} \frac{b-a}{ab} \end{bmatrix}$