Find the volume of the described solid S.
a.The base of S is a circular disk with radius r.Parallel cross-sections perpendicular to the base are squares.
b.The base of S is the triangular region with vertices (0, 0), (1, 0) and (0, 1). Cross-sections perpendicular to the y-axis are equilateral triangles.
c.The base of S is the region enclosed by the parabolaand the x
-axis.Cross-sections to the y-axis are squares.