Figure 5-4 A graph of price, P, versus quantity, Q, is a demand curve, Demand, consisting of a straight line descending from upper left to lower right. Curve Demand = P sub max minus m times Q. Two following points are shown, for convenience called Point 1 and Point 2, where Point 1 is to the right of Point 2. Point 1 is at (Q 1, P 1), and Point 2 is at (Q 2, P 2). The area under Curve Demand bounded by the lines P = P 2, Curve Demand, and Q = Q 1, form a vertical rectangle with the upper right corner snipped at the angle of Curve Demand. The area may be subdivided into four segments, an upper left rectangle, A, a lower left rectangle, B, an upper right triangle, C, and a lower right rectangle, D. Starting at the upper left and going clockwise, the vertices of Rectangle A are (0, P 2), (Q 2, P 2), (Q 2, P 1), and (0, P 1). The vertices of Rectangle B are (0, P 1), (Q 2, P 1), (Q 2, 0), and (0, 0). The vertices of Triangle C are (Q 2, P 2)