A magnetic field of 2×10⁻² T acts at right angles to a coil of area 100 cm⁻² with 50 turns. The average emf induced in the coil is 0.1 V, when it is removed from the field in time t. The value of t is
(a) 0.1 sec
(b) 0.01 sec
(c) 1 sec
(d) 20 sec