Diagrams A,B,and C Show 3 Individual Consumers' Demand Curves for Cement.Consumers

Multiple Choice

Diagrams A,B,and C show 3 individual consumers' demand curves for cement.Consumers A,B,and C constitute the entire monthly cement market in this region. FIGURE 6-3
-Refer to Figure 6-3.On the regional market demand curve for cement (not shown) ,at which price level(s) is there a "kink" in the demand curve?

A) $10
B) $20 and $30
C) $30 and $70
D) $40 and $70
E) $80