Final answer:
The correct response is 'e. None of the above.' When average product is at its maximum, there is no direct implication that marginal cost, marginal revenue product, or average variable cost are at their minimum or maximum.
Step-by-step explanation:
When average product is at its maximum, none of the given options necessarily coincide with this situation. According to microeconomic theory, particularly the analysis of production and costs in the short run, different measures of productivity and cost have distinct relationships. When average product is at its maximum, it does not mean that marginal cost, marginal revenue product, average variable cost, or any other cost measure is at its minimum or maximum. The marginal cost is at its minimum where the marginal cost curve crosses the average variable cost curve from below, which is the shutdown point, not necessarily where the average product is at its maximum.
When the average product is at its maximum, it implies that the firm is producing the optimal level of output where the marginal product is equal to average product. This also means that the marginal cost is at its minimum. Therefore, the correct answer is (c) Marginal cost is at its minimum.