(d) 28 gallons Let, the initial amount of liquid soap be 'x' gallons. Ratio of the liquid soap left in the container to that of water = 1336​ ∴ Amount of liquid soap left = 4936x​ Now, according to formula,4936x​=x(1−x4​)2 ⇒ 76​=xx−4​ ⇒ 76x​ = x - 4∴ x = 28 gallons.