Two pipes A and B can fill an empty cistern in 1.8 and 2.7 hours, respectively. Pipe C can drain the entire cistern in 4.5 hours when no other pipe is in operation. Initially when the cistern was empty Pipe A and Pipe C were turned on. After a few hours, Pipe A was turned off and Pipe B was turned on instantly. In all it took 5.5 hours to fill the cistern. For how many hours was Pipe B turned on?

• A. 5
• B. 4.5
• C. 3
• D. 2.7