1. The problem statement, all variables and given/known data A pile of earth standing on flat ground near an abandoned mine has height 13 meters. The ground is the xy-plane; the origin is directly below the top of the pile and the z-axis is upward. The cross-section at height z is given by [tex]x^2 + y^2 = 13 - z[/tex] for [tex]0 \leq z \leq 13[/tex] with x, y, and z in meters. (a) What equation gives the edge of the base of the pile? (b) What is the area of the base of the pile? 2. Relevant equations 3. The attempt at a solution I really don't know what it means by the edge of the base of the pile, I know that after we get to part a. then the area is just the integral right?