Figure 4-1 A demand curve, D, of price, P, versus quantity, Q, is a straight line descending from point (0, maximum price) to (maximum quantity, 0). From left to right, a Point A and a Point B are shown on the demand curve. The coordinates for Point A are (Q, P), and the coordinates for Point B are (Q prime, P prime). Refer to Figure 4-1. The movement from point A to point B on the graph is caused by an increase in price. a decrease in price. a decrease in the price of a substitute good. an increase in income