A Series RL Circuit with Inductance 6 $\Omega$ Is Connected to a 12

Multiple Choice

A series RL circuit with inductance 6.0 mH and resistance 20 $\Omega$ is connected to a 12.0-V battery of negligible internal resistance. The rate of change of current in the circuit 4.0 $\mu$ s after the switch is closed is

A) 2.0 * 10³ A/s.
B) 1.0 * 10³ A/s.
C) 7.2 A/s.
D) 3.0 A/s.
E) 0.60 A/s.