Marginal product is the change in total output resulting from a one-unit change in which input?

• A. Labor
• B. Capital
• C. Price
• D. Cost

Answer: (C)

Marginal product shows how much total output changes when you add one more unit of an input. In production analysis, the most common example is labor: the marginal product of labor is the extra output you get from hiring one additional worker, calculated as ΔQ/ΔL. Price and cost aren’t inputs to the production process themselves—they’re market outcomes and expenses, respectively. Capital can be an input too, but in the short run it’s often fixed, so the usual focus is on labor. So the input whose one-unit change changes output is labor.