1.9. Evaluate each of the following statements. If a statement is true, explain why; if it is false, identify the mistake and try to correct it.

a. A decreasing marginal product tells us that marginal cost must be rising.

b. An increase in fixed cost increases the minimum-cost output.

c. An increase in fixed cost increases marginal cost.

d. When marginal cost is above average total cost, average total cost must be falling.