Mathematically, the marginal cost function is expressed as the gradient of the total cost (TC) function with respect to quantity. Note that the marginal cost may change with density, and so at each level of production, the marginal cost is the cost of the last unit produced. | Mathematically, the marginal cost function is expressed as the gradient of the total cost (TC) function with respect to quantity. Note that the marginal cost may change with density, and so at each level of production, the marginal cost is the cost of the last unit produced. |