The following data relate to a firm's production: Fixed cost = ₦120,000; Variable cost at 300 units = ₦180,000; Variable cost at 301 units = ₦181,500. What is the marginal cost of the 301st unit?

Marginal cost is the change in total cost (or equivalently, the change in total variable cost) from producing one additional unit. MC = ₦181,500 − ₦180,000 = ₦1,500. Fixed costs do not change with output and are therefore irrelevant to the marginal cost calculation.