A standard cylindrical tube of tennis balls fits three tennis balls. The diameter of a tennis ball is 6.9 cm. The bottom and side of the tube is made of plastic while the lid is made of aluminum )see picture on next page). How much plastic and aluminum is needed if the cylinder is just large enough to fit all three balls? Then, find out the volume of unfilled space in the tube and express this as a percentage of the total volume of the tube.