The problem says:
A swimming pool is circular with a 40-ft diameter. The depth is constant along east-west lines and increases linearly from 2ft at the south end to 7ft at the north end. Find the volume of water in the pool.
The approach I would think would be to see this as finding the volume under a plane with the bounds and
I'm having trouble finding the equation of this plane. I would think two points are (0,20,7) and (0,-20,2). However, I'm having trouble finding a third point. I know that from three points I can find two vectors, then a normal vector, and then the equation of the plane.