Question 760080
5.4km/hr = 90m/min
If we give the water a length of 1 metre
the volume will be 2 x 20 x 1 = 40 m^3
Running at 90m/min 
In 3 mins = 90 * 40 * 3
= 10800m^3 in 3 mins
Hope this helps.
:-)