sentences:  Given a monotone decreasing probability density function "f"("x"), defined for all "x" ≥ 0, the base of the ziggurat is defined as all points inside the distribution and below "y"1 = "f"("x"1).This consists of a rectangular region from (0, 0) to ("x"1, "y"1), and the (typically infinite) tail of the distribution, where "x" > "x"1 (and "y" < "y"1).This layer (call it layer 0) has area "A".