A concavely upward increasing line and three parallel decreasing lines are presented on a coordinate plane.The horizontal axis is labeled real output in quantity in billions per year and it ranges from 0 to 20 in increments of 2. The vertical axis is labeled price level in average price and it ranges from 20 to 40 in increments of 2. The concavely upward increasing curve is labeled A S. It starts from (2 comma 25), rises concavely upward through (8 comma 26), (11 comma 27), (15 comma 30), and ends at the point (17 comma 36). The first decreasing line is labeled A D sub 1. It starts from (2 comma 31), intersects the curve at (8 comma 26), and ends at (13 comma 22). The second decreasing dashed line is labeled A D sub 2. It starts from (2 comma 34.5), intersects the curve at (11 comma 27), passes through (12 comma 26), and ends at (16 comma 23). The third decreasing dashed line is labeled A D sub 3. It starts from (6 comma 38), intersects the curve near (15 comma 30), passes through (19 comma 27), (20 comma 26). Vertical and horizontal dashed lines are drawn from