Final answer:
The subject of this question is supply. The curve that shows the marginal cost of producing one more unit of a good or service is a key concept in economics and is represented by the supply curve. The marginal cost represents the additional cost incurred for producing one more unit of a good or service.
Step-by-step explanation:
The curve that shows the marginal cost of producing one more unit of a good or service is a key concept in economics and is represented by the supply curve. The marginal cost represents the additional cost incurred for producing one more unit of a good or service. It is important for producers to consider marginal costs when making production decisions, as it helps them determine the optimal level of output.