Two pipes A and B can fill an empty tank in 8 hours and 12 hours respectively. They are opened alternately for 1 hour each, starting with pipe A first. In how many hours will the empty tank be filled?

Two pipes A and B can fill an empty tank in 8 hours and 12 hours respe

1.	Two pipes A and B can fill an empty tank in 8 hours and 12 hours respectively. They are opened alternately for 1 hour each, starting with pipe A first. In how many hours will the empty tank be filled?
A.	\(9\frac{1}{4}\)
B.	9
C.	\(9\frac{1}{3}\)
D.	\(9\frac{1}{2}\)
Answer» E.