Q. Two pipes A and B can fill a tank in 36 min. and 45 min. respectively. Another pipe C can empty the tank in 30 min. First A and B are opened. After 7 minutes, C is also opened. The tank filled up in:

• A. 39 min.
• B. 46 min
• C. 40 min.
• D. 45 min.

Correct Answer: B