1. The problem statement, all variables and given/known data What happens when an infinitely tall vertical rectangular prism consisting of all (x,y,z) with x between a and b and y between c and d is cut by a non-vertical plane z = px + qy + k? What are the possible shapes of the slice? 2. Relevant equations I don't know...no idea really 3. The attempt at a solution I think it would be a parallelogram, but I have no idea how to prove this.