Pipes A and B can fill a tank in 5 and 6 hours respectively. Pipe C can empty it in 12 hours. If all the three pipes are opened together, then the tank will be filled in?	Choices.
A) 1 13/17 hours
B) 2 8/11 hours
C) 3 9/17 hours
D) 4 1/2 hours
E) NONE
Net part filled in 1 hour = 1/5 + 1/6 - 1/12 = 17/60   The tank will be full in 60/17 hrs, i.e., 3 9/17 hrs.   ANSWER:3 9/17 hours
<result>C</result>
Pipes A and B can fill a tank in 5 and 6 hours respectively. Pipe C can empty it in 12 hours. If all the three pipes are opened together, then the tank will be filled in?