A long solenoid of radius 1 mm has 100 turns per mm. If 1A current flows in the solenoid, the magnetic field strength at the center of the solenoid is
(1) 12.56 x 10⁻² T
(2) 12.56 x 10⁻⁴ T
(3) 6.28 x 10⁻⁴ T
(4) 6.28 x 10⁻² T