A fuel-oil tank is 10 feet long and has flat ends that are perpendicular to the ground surface. Cross-sections parallel to the flat ends have the shape of the ellipse x2/9 + y2/36 = 1. If the fuel oil in the tank is 9 feet deep, what is the volume of the fuel oil in the tank?
Show the integrals you use to solve this problem. You MAY do a numerical integration, rather than applying the Fundamental Theorem.