The water level in a rectangular swimming pool measuring 40 feet by 25 feet is to be lowered by 6 inches. How many gallons of water must be removed? (1 cu ft = 7.5 gallons)  Choose the correct answer.
A) 100	B) 250	C) 750	D) 3750	E) 5625

Rationale: "6 inches = 1 / 2 feet ( there are 12 inches in a foot . ) , so 40 * 25 * 1 / 2 = 500 feet ^ 3 of water must be removed , which equals to 500 * 7.5 = 3750 gallons . answer : d ."
Answer: D