Answer:
time=4s
Explanation:
we know that in a RL circuit with a resistance R, an inductance L and a battery of emf E, the current (i) will vary in following fashion
, where
max=
Given that, at i(2)=
⇒
⇒
⇒
Applying logarithm on both sides,
⇒
⇒
⇒
Now substitute 
⇒
⇒
⇒
Applying logarithm on both sides,
⇒
⇒
⇒
now subs. 
⇒
also 
⇒
⇒
<em>Hope this will help u</em><em>.</em><em>.</em><em>.</em><em>.</em><em>.</em><em>✌</em><em>✌</em><em>✌</em>
The answer is C! I knew this way before taking the test

P = Power
W = Work
Delta T = Change of Time
So:
P = 35 Joules
Delta T = 70 secs
W = ?

* Joule/Sec = Watt
Answer: The power used to do this task was 0.5 Watts.