Acertain cylindrical tank holds 20,000 gallons of water which can be drained from the bottom of the tank in 20 minutes the volume tea of water remaining in the tank after t minutes is given by the function (v)= 20,000(1-(t/20)^2 where b is in gallons zero is less than or equal to t which less than or equal to 20 is in a minutes and t equals zero represent the instant the tank starts draining how fast is the water draining 4 1/2 minutes after it begins