20. What is the relationship between the law of diminishing returns and the marginal cost curve? (check all that apply) (p. 536) a. The law of diminishing returns is a consequence of the shape of the marginal cost curve. b. The law of diminishing returns explains the shape of the marginal cost curve. c. The shape of the marginal cost curve is a consequence of the law of diminishing returns. d. There is no relationship between the two