Two air-cored coils, A and B, are wound with 100 and 500 turns respectively. A current of 5 A in A produces a flux of 15 Wb. Calculate
(a) the self-inductance of coil A,
(b) the mutual inductance, if 75% of the flux links with B, and
(c) the emf induced in each of the coils, when the current in A is reversed in a time of 10 ms.