Pipe A can fill a tank in 2 hours. Due to a leak at the bottom, it takes 4 hours for the pipe A to fill the tank. In what time can the leak alone empty the full tank?	Select the correct option
A) 2  B) 5  C) 6  D) 4  E) 1

Rationale: "let the leak can empty the full tank in x hours 1 / 2 - 1 / x = 1 / 4 = > 1 / x = 1 / 2 - 1 / 4 = 1 / 4 = > x = 4 . answer : d"
Answer: D