A cone is cut out of the center of a pyramid with a rectangular base. The rectangular base has side lengths of 15 and 10 units. The cone has a diameter of 9 and a height of 12. The pyramid and cone have the same height. What is the volume of the shaded portion of the composite figure? Express your answer in terms of π. 519π units3 681π units3 (600π – 81) units3 (600 – 81π) units3