When the current in a certain inductor coil is 5 A and is increasing at the rate of 10 A/s, the potential difference across the coil is 140 V. When the current is 5 A and decreasing at the rate of 10 A/s, the potential difference is 60 V. The self-inductance of the coil is
(a) 2 H
(b) 8 H
(c) 4 H
(d) 12 H
