the figure above represents a square sheet of cardboard with side length 20 inches. the sheet is cut and pieces are discarded. when the cardboard is folded, it becomes a rectangular box with a lid. the pattern for the rectangular box with a lid is shaded in the figure. four squares with side length x and two rectangular regions are discarded from the cardboard. which of the following statements is true? (the volume v of a rectangular box is given by v