Perfect competition displays because the social benefits of additional production, as measured by the price that people are willing to pay, are in balance with the to society of that production.

allocative efficiency; marginal costs

Explanation:allocative efficiency is at an output level where the Price equals the Marginal Cost (MC) of production. This is because the price that consumers are willing to pay is equivalent to the marginal utility that they get. Therefore the optimal distribution is achieved when the marginal utility of the good equals the marginal cost.

The marginal cost is the cost of producing one additional item and is used to pinpoint the optimal economy of scale. The marginal benefit is the greater enjoyment created by producing one additional item.

answer; someone must cover the cost associated with the provision of scarce goods in both sectors;