Unfortunately though, I think in order to answer these cases in the problem, I think we should have been given with the volume of each of the aquarium. However, generally, the approach to this problem is to simply divide the volume by the number of fish and see if it meets the guideline. We will know that it meets the guideline if the quotient obtained is greater than or equal to 1 cubic foot per 4 fish. Solving for the minimum volume of each of the Aquariums,
(A) Aquarium A: 60 fish x (1 ft³ / 4 fish) = 15 ft³
(B) Aquarium B: 200 fish x (1 ft³ / 4 fish) = 50 ft³
(C) Aquarium C: 50 fish x (1 ft³ / 4 fish) = 12.5 ft³