A and B can fill a tank in 12 hours and 20 hours respectively while Pipe C can empty it in 15 hours. They all are opened together. After 5 hours, efficiency of A and B are increased by 20% and 100% respectively and efficiency of C is decreased by 50%. Find the total time taken to fill the tank if it is completely empty in the start.
1
6 hours
2
7 hours
3
8 hours
4
9 hours
5
10 hours