Two concentric circular coil,s one of small radius `r_(1)` and the other of large radius `r_(2)`, such that `r_(1) lt lt r_(2)`, are placed co-axially with centres coinciding. Obtain the mutual inductance of the arrangement.

Options

A. `R_(1)//R_(2)`
B. `R_(2)//R_(1)`
C. `R_(1)^(2)//R_(2)`
D. `R_(2)^(2)//R_(1)`