Q: How long will it take for two pipes A and B to fill an empty cistern if they worked alternately for an hour each ? A. Working alone, Pipe A can fill the cistern in 40 hoursB. Pipe B is one third as efficient as Pipe A

• A. Only A is sufficient
• B. Only B is sufficient
• C. Both (A) and (B) are sufficient
• D. and (B) are sufficient D)