A pump can fill a tank with water in 2 hours. Because of a leak, it took 2 1/7 hours to fill the tank. The leak can drain all the water of the tank in?
Select:	A) 17 hr	B) 19 hr	C) 10 hr	D) 24 hr	E) 30 hr

Rationale: "work done by the tank in 1 hour = ( 1 / 2 - 2 1 / 7 ) = 1 / 30 leak will empty the tank in 30 hrs . answer : e"
Answer: E