3. S lies between the two surfaces z = x² + y² and z = 9-x²-y². Sketch S and use a triple integral to calculate its exact volume, showing all your steps.

A soda can has a volume of 25 cubic inches. Let x denote its radius and h its height, both in inches. a. Using the fact that the volume of the can is 25 cubic inches, express h in terms of x. b. Express the total surface area S of the can in terms of x.