A bar magnet is demagnetized by inserting it inside a solenoid of length 0.2 m, 100 turns, and carrying a current of 5.2 A. The coercivity of the bar magnet is:

a) 0.25 A/m
b) 0.20 A/m
c) 0.30 A/m
d) 0.15 A/m