What Is the Inductance of a Series RL Circuit in Which

Multiple Choice

What is the inductance of a series RL circuit in which R = 1.0 K $\Omega$ if the current increases to one-third of its final value in 30 $\mu$ s?

A) 74 mH
B) 99 mH
C) 49 mH
D) 62 mH
E) none of the above