Answer:
40 minutes
Explanation:
We have a load and a discharge, given by a speed that would be a barrel / minute.
Which means that the loading rate is: 1/20
And the discharge rate: 1/40
Since they are contrary, the result would be the subtraction between these two rates:
1/20 - 1/40 = 1 / x
1 / x = 0.025
x = 1 / 0.025
x = 40
Which means it will take 40 minutes to fill under the mentioned conditions