You can put this solution on YOUR website! 1 foot = 12 inches (you can't mix apples and oranges. It's inches with inches)
4.5^2(Pi) = 20.25Pi = 63.617
and
63.617*24 = 1,526.81 cubic inches
Convert to liters and you get 25 liters (conversion table must be in your book, if not google it).