Pipes A and B can fill a tank in 5 and 7 hours. Pipe C can empty it in 12 hours. If all pipes are opened together, then the tank will be filled in?  Choose the most appropriate option
A) 27/7 hr	B) 17/19 hr	C) 52/11 hr	D) 6 hr	E) 63/19 hr
Net part filled in 1 hour = 1/5 + 1/7 - 1/12 = 7/27   The tank will be full in 27/7 hr   27/7 hrnswer is 27/7 hr
<result>A</result>
Pipes A and B can fill a tank in 5 and 7 hours. Pipe C can empty it in 12 hours. If all pipes are opened together, then the tank will be filled in?