Which statement best illustrates the law of diminishing returns?
a. The average total cost of the last unit of a resource used is less than the average total cost of the previous resource used
b. The marginal product of the last unit of a resource used is less than the marginal product of the previous resource used
c. The average product of the last unit of a resource used is less than the average product of the previous resource used
d. The marginal cost of the last unit of a resource used is less than the marginal cost of the previous resource used