Pipe A is an inlet pipe that can fill an empty cistern in 8.7 hours. Pipe B can drain a filled cistern in 5.8 hours. When the cistern was filled the two pipes are opened one at a time for an hour each, starting with Pipe B. How long will it take for the cistern to be empty?

A

32 hours 16 minutes

B

30 hours 48 minutes

C

32 hours

D

31 hours