A Pair of coils of turns `n_(1)` and `n_(2)` are kept close together. Current passing

A Pair of coils of turns `n_(1)` and `n_(2)` are kept close together. Current passing through the first is reduced at r, and emf 3 mV is developed across the other coil. If the second coil carries current which is then reduced at the rate 2 r, the emf produced across the first coil will be