A pump has moved V(t)=t3−6t2+9t+20 liters of water into a tank t minutes after it is turned on.
a) Determine the instantaneous pumping rate at t=5 minutes.
b) Calculate the average pumping rate over the interval 4≤t≤5 minutes and state whether the instantaneous rate at t=5 is greater than, less than, or equal to this average rate. Include units and a brief interpretation.