An 80-MH Inductor and a 2 $\Omega$ Resistor Are Wired in Series to an Ideal Battery

Multiple Choice

An 8.0-mH inductor and a 2.0- $\Omega$ resistor are wired in series to an ideal battery. A switch in the circuit is closed at time 0, at which time the current is 0. The current reaches half its final value at a time of:

A) 2.8 ms
B) 4.0 ms
C) 3 s
D) 170 s
E) 250 s