A frustum is formed when a plane parallel to a cone's base cuts off the upper portion as shown. A cone is shown. The top of the cone is cut off to form a frustum of the bottom portion. The cone has a radius of 3.5 and a height of 8. The frustum has a height of 11 and a radius of 7.5. Which expression represents the volume, in cubic units, of the frustum? One-thirdπ(7.52)(11) – One-thirdπ(3.52)(8) One-thirdπ(7.52)(11) + One-thirdπ(3.52)(8) One-thirdπ(7.52)(19) – One-thirdπ(3.52)(8) One-thirdπ(7.52)(19) + One-thirdπ(3.52)(8)