Final answer:
The correct answer is option a. The amount that an additional unit of a factor adds to a firm's total revenue is called the value of the marginal product.
Step-by-step explanation:
The correct answer is a. value of the marginal product.
The amount that an additional unit of a factor adds to a firm's total revenue is called the value of the marginal product. It represents the additional revenue that a firm earns by using one more unit of a factor of production, such as labor or capital. This concept is used to determine how much a firm should pay for an additional unit of a factor of production, based on the additional revenue it generates.
For example, if hiring one more worker increases a firm's total revenue by $100, then the value of the marginal product of that worker is $100. By comparing the value of the marginal product to the cost of hiring an additional worker, a firm can determine whether it is profitable to do so.