In the context of copper production, the area representing deadweight loss on a supply and demand graph is created due to the market producing at a quantity where the marginal social cost exceeds the marginal social benefit, resulting in a loss of economic efficiency. This inefficiency is characterized by the gap between the socially optimal quantity and the actual quantity produced, leading to a reduction in overall societal welfare. The deadweight loss can be represented as a triangle formed between the supply and demand curves. The key term that best describes the quantity where marginal social cost equals marginal social benefit is __________.

The key term that best describes the quantity where marginal social cost equals marginal social benefit is "socially optimal quantity. " This is the point where the costs to society of producing an additional unit of copper are exactly balanced by the benefits that society receives from that unit. When production is at this optimal level, there is no deadweight loss, meaning resources are used efficiently, and society gains maximum welfare. For example, if a factory produces copper at a level where the cost of environmental damage outweighs the benefits of the copper produced, it creates inefficiency and a deadweight loss. Thus, achieving the socially optimal quantity is essential to ensure that the production of copper benefits society as a whole.