The approximate formula expressing the formula of mutual inductance of two coaxial loops of the same redius `a` when their centers are separated by a distance `l` with `l gt gt a` is
A. `(1)/(2) (mu_(0)pia^(4))/(l^(3))`
B. `(1)/(2) (mu_(0)a^(4))/(l^(2))`
C. `(mu_(0))/(4pi) (pia^(4))/(l^(2))`
D. `(mu_(0))/(pi) (a^(4))/(l^(3))`