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 same cruurent I is placed parallel to z - axis and passing through point (0,b,0), (b >>a). The magnitude of troque on the loop about z - axis will be :

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)`