Does anybody know how to start to workout this problem? The region of the base of the solid is bounded by y=abs(x)+3 and y=x^2-9, with parameters x=0 and x=4. Each cross-section is a square with its diagonal on the base. It also asked something about using Rieman Sums to solve this problem. I made the solid using foams and it looked like a hoof-shaped base embeded in squares. Thanks for any help.