Not only can consumers have more choices in the price, variety and service of commodities, but also make it better for enterprises to purchase production factors and sales products. "We are concerned that if the UK decides to leave, it is likely to lead to a weaker pound, higher inflation, lower disposable income and less investment," she said. It is not obvious in some analyses, but it is important to note that economic profits include opportunity costs. The profit of an entrepreneur (normal profit) is usually positive, but economic profit can be either positive or negative (loss). That's why the opportunity cost is included: in a completely competitive market, when marginal cost equals marginal revenue, profit maximization or loss minimization conditions arise. If the market price is lower than the total average cost, which means that the economic profit is negative, the entrepreneur needs to compare the value of the loss and the average variable cost. If the business continues to operate, the negative economic profit must not be lower than the average variable cost, otherwise the entrepreneur would rather shut down the company than continue to take the loss. At present, about the nature of the enterprise. Western economists have different views. There is also some debate. Some western economists analyze the nature of the enterprise mainly from the perspective of transaction costs that coase emphasizes. The theory of modern political economy in China holds that the profit under the socialist system is the form of the value of the surplus products created by the workers for the society. The value composition of the product is c+v+m,c+v is converted into production cost, and the m is part of the surplus product created by the laborer for the society, which translates into profit for the enterprise. The specific form of socialist profit is: to realize profit, that is, the balance of the sales revenue of the enterprise minus the expenses of various expenses; To pay the profits in accordance with the provisions to the national financial department; After tax profit, that is, the profit of the enterprise shall be returned to the enterprise in accordance with the state provisions.