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 :
A. 2μ₀I²a²/πb
B. 2μ₀I²a²b/π(a²+b²)
C. μ₀I²a²b/2π(a²+b²)
D. μ₀I²a²/2πb