There is a conducting ring of radius `R`. Another ring having current `i` and radius `r (r lt lt R)` is kept on the axis of bigger ring such that its center lies on the axis of bigger ring at a distance `x` from the center of bigger ring and its plane is perpendicular to that axis. The mutual inductance of the bigger ring due to the smaller ring is
A. `(mu_(0)piR^(2)r^(2))/((R^(2)+x^(2))^(3//2)`
B. `(mu_(0)piR^(2)r^(2))/(4(R^(2)+x^(2))^(3//2)`
C. `(mu_(0)piR^(2)r^(2))/(16(R^(2)+x^(2))^(3//2)`
D. `(mu_(0)piR^(2)r^(2))/(2(R^(2)+x^(2))^(3//2)`
