When the current in the primary coil of 400 turns of a magnetic circuit, enhances linearly from10mA to 35mA in 100ms, an e.m.f. of 75mV is induced into the secondary coil of 240 turns, which is left open circuited. Determine
(a) The mutual inductance of the two coils,
(b) The reluctance of the former, and
(c) The self inductance of the secondary coil.