The Magnetic Field at Any Point in the Xy Plane $\pi$

Multiple Choice

The magnetic field at any point in the xy plane is given by , where is the position vector of the point, A is a constant, and is a unit vector in the +z direction.The net current through a circle of radius R, in the xy plane and centered at the origin is given by:

A) " $\pi$ AR²/ $\mu$ ₀"
B) "2 $\pi$ AR/ $\mu$ ₀"
C) "4 $\pi$ AR³/3 $\mu$ ₀"
D) "2 $\pi$ AR²/ $\mu$ ₀"
E) " $\pi$ AR²/2 $\mu$ ₀"