66 The base of S is a circular disk with radius r Parallel cross sections perpendicular to the base are squares 67 The base of S is an elliptical region with boundary curve 9x 4y 36 Cross sections perpendicular to the z axis are isosceles right triangles with hypotenuse in the base Answer 68 The base of S is the triangular region with vertices 0 0 1 0 and 0 1 Cross sections perpendicular to the y axis equilater