Correct Answer - Option 3 : 60 min

__Concept:__

The capacity of the battery is represented in terms of Amp-hour.

The capacity of battery = current delivered × duration of time

Battery capacity unit mAh means when 1 mA of current is drawn from a battery it will take 1 hour to discharge.

__Calculation:__

The capacity of battery = 4000 mAh

Current delivered = 4 A

\(Duration \ of \ time = \frac{4000 \ mAh}{4 \ A}\)

\(T = \frac{4000\times10^{-3}h}{4 \ A}=1 \ hour\)

T = 60 min