Chapter 1, Problem 1DQ

this answer is incorrect. please stop giving me incorrect answers.

Please answer the questions below thank you. Just give the letter of the correct answer no need to give solutions.

I believe the solution to the problem at this url is incorrect and that the problem requires integration. I asked this problem once before and got a very different answer (64 gallons versus 11 gallons as provided in this answer). The previous solution was much more involved but I had a hard time following the solution so I asked the question again. I would like this problem solved by a different expert please.    https://www.bartleby.com/questions-and-answers/5.-oil-flows-into-a-tank-according-to-the-rate-ft11-and-at-the-same-time-empties-out-at-the-rate-et-/cdf8b9dc-0b1c-4bfc-bb53-ad200f80692b