An outlet pipe empties a tank which is full in 10 hours. If the inlet pipe is kept open, which lets water in at the rate of 16 litres/min then outlet pipe would take 8 hours longer. Find the capacity of the tank.	Pick one.
A) 8600 litres
B) 200 litres
C) 21600 litres
D) 11200 litres
E) 13200 litres

Rationale: "let the rate of outlet pipe be x liters / hour ; rate of inlet pipe is 16 litres / min , or 16 * 60 = 960 liters / hour ; net outflow rate when both pipes operate would be x - 960 liters / hour . capacity of the tank = x * 10 hours = ( x - 960 ) * ( 10 + 8 ) hours 10 x = ( x - 960 ) * 18 - - > x = 2160 - - > capacity = 10 x = 21600 liters . answer : c ."
Answer: C