A frustum (truncated cone), and the formula for determining its volume, is shown below. The radius (r) of the frustum’s upper base is 9 feet. The radius (R) of the frustum’s lower base is 15 feet. The height of the frustum is 8 feet and the slant height of the frustum is 10 feet. What is the volume of the frustum? (Note: A common mistake for this solid is to call it a “frustrum”; however, the correct term is “frustum”.)