A square loop of side 2a, and carrying current I, is kept in XZ plane with its centre at origin. A long wire carrying the samecurrent I is placed parallel to the z-axis and passing through the point `(0,b, 0)`, (b >> a). The magnitude of the torque on the loop about z-axis is given by :

Options

A. `(2 mu_0 I^2 a^2)/(pib)`
B. `(2mu_0 I^2a^2b)/(pi(a^2+b^2))`
C. `(mu_0I^2a^2b)/(2pi(a^2 + b^2))`
D. `(mu_0I^2a^2)/(2pib)`