A water tank has been fitted with two taps P and Q and a drain pipe R. Taps P and Q fill at the rate of 12 litres per minute and 10 litres per minute respectively. 
Consider the following statements SI, S2 and S3 : 
S1 : Pipe R drains out at the rate of 6 litres per minute. 
S2 : If both the taps and the drain pipe are opened simultaneously, then the tank is filled in 5 hours 45 minutes. 
S3 : Pipe R drains out (fully) the filled tank in 15 hours 20 minutes. 
To know what is the capacity of the tank, which one of the following is correct?