Pipe A can fill a tank in 10 hours. Due to a leak at the bottom, it takes 15 hours for the pipe A to fill the tank. In what time can the leak alone empty the full tank?  Choose the correct choice from the following choices.
A) 76
B) 84
C) 56
D) 75
E) 30
Let the leak can empty the full tank in x hours 1/10 - 1/x = 1/15   =&gt; 1/x = 1/10 - 1/15 = (3 - 2)/30 = 1/30   =&gt; x = 30.   Answer: 30
<result>E</result>
Pipe A can fill a tank in 10 hours. Due to a leak at the bottom, it takes 15 hours for the pipe A to fill the tank. In what time can the leak alone empty the full tank?