A cistern has two pipes. One can fill it with water in 8 hours and other can empty it in 5 hours., In how many hours will the cistern be emptied if both the pipes are opened together when 3/4 of the cistern is already full of water ?

• A. 13(1/3) hours
• B. 10 hours
• C. 6 hours
• D. 3(1/3) hours