Pipes A and B can fill a tank in 2 and 3 hours. Pipe C can empty it in 6 hours. If all pipes are opened together, then the tank will be filled in?	Select the correct option:
A) 3/2hr  B) 1/2hr  C) 1hr  D) 9/7hr  E) 5/3hr
Net part filled in 1 hour = 1/2 + 1/3 - 1/6 = 2/3   The tank will be full in 3/2 hr   Answer is 1/2hr
<result>B</result>
Pipes A and B can fill a tank in 2 and 3 hours. Pipe C can empty it in 6 hours. If all pipes are opened together, then the tank will be filled in?