An overhead tank is connected by 3 pumps A, B and C. The pumps A and B can fill the tank in 4 hours and 5 hours respectively, where a C can empty the Tank in 2 hours. If A. B and C are opened in order at 5.00 am; 6.00 am and 7.00 am when will the tank be empty?

A

6 pm

B

7 pm

C

8 pm

D

9 pm