Final answer:
The additional production from the use of one more unit of variable input is called the marginal product, which helps determine optimal production levels.
Step-by-step explanation:
The additional production yielded by the use of one extra unit of variable input is known as the marginal product. The marginal product is the extra output or change in the total product that results from the addition of one more unit of variable input, such as labor. By analyzing changes in marginal product during various stages of production, businesses can determine the optimal number of resources and inputs to use to produce at an optimal level. This considers increasing returns, diminishing returns, and negative returns to calculate the most efficient usage of input variables.