A circular coil of radius R carries an electric current. The magnetic field due to the coil at a point on the axis of the coil located at a distance r from the center of the coil, such that r from the center of the coil, such that r > > R, varies as
(a) 1/r
(b) 1/r³/²
(c) 1/r²
(d) 1/r³
