Three taps P, Q and R are filled in a water tank to draw out water. Tap P fills 4 buckets in 24 minutes, Q fills 8 buckets in 1 hour and R fills 2 buckets in 20 minutes. All the taps are opened and the tank is emptied in 2 hours. If a bucket holds 10 litres of water, what is the capacity of the tank?
1
180 litres
2
240 litres
3
480 litres
4
200 litres