Panel (a) shows the effect of an increase in the price of wheat on George and Martha’s demand for labor. The value of the marginal product of labor curve shifts upward, from VMPL1 to VMPL2. If the market wage rate remains at $200, profit-maximizing employment rises from 5 workers to 8 workers, shown by the movement from point A to point B. Panel (b) shows the effect of a decrease in the price of wheat. The value of the marginal product of labor curve shifts downward, from VMPL1 to VMPL3. At the market wage rate of $200, profit-maximizing employment falls from 5 workers to 2 workers, shown by the movement from point A to point C.