Final answer:
The optimal employment of an input occurs when its marginal revenue product (MRP) is equal to both its price and its marginal factor cost (MFC), hence the correct answers are (c) and (d), making option (e) the final correct option.
Step-by-step explanation:
The question at hand is related to input employment in economics, specifically within the context of a firm's production and the associated cost. The optimal employment of an input occurs when the marginal revenue product (MRP) is equal to its price, which is also the input's marginal factor cost (MFC).
Therefore, options (c) MRP is equal to its price and (d) MRP is equal to its MFC are both correct. This assertion is supported by the principle that a profit-maximizing firm in a perfectly competitive market will increase production as long as the marginal revenue (MR) exceeds marginal cost (MC).
However, the firm will cease expanding production when MR equals MC, to prevent economic profit decline. For a perfectly competitive firm, MR is equivalent to price (P), which aligns with MRP for an input.
In the case of Table 8.1, maximum profit occurs at an output level between 70 and 80 units because that is the range where MR is greater than or equal to MC. The discrepancy between the profit levels at Q = 70 and Q = 80 can be explained by the fact that profits remain the same across this range, yet hitting the MR = MC condition at 80 units signals the firm to stop expanding production to maintain maximum profit levels.
To directly answer the student's question, the correct option in the final answer is (e) both (c) and (d) above are correct.