difference between net sales and gross profit The market is the economic contact method which is the basic content of Commodity Exchange. Under the condition of commodity economy, the premise of exchange generation and existence is social division of labor and commodity production. Because of the social division of labor, the different producers, respectively, engaged in the production of different products, did not meet the needs of themselves and others and exchange their respective product, so that the general labor products into commodities, make the product production is transformed into commodity production. It is under this condition that the market for goods to be exchanged to meet the needs of different producers is born. Therefore, the market is the product of the division of labor and the exchange of goods under the conditions of commodity economy. The market and commodity economy have inalienable internal relation. (1) spiritual gain -- spiritual satisfaction; While many key factors need to be taken into account when making plans, the core issue always is when to exit the transactions that have been entered. This actually includes three exit plans. For one thing, there must be a plan to accept losses, and to pull out if the deal loses. Second, there must be a plan to accept a profit, and once the profit target is met, it will be satisfied. Third, there must be a plan that allows the trader to exit the transaction in the event that a significant change is not occurring for a considerable period of time. Full market competition will make economic activity full of vigor and vitality. From the end of the 19th century to the early 20th century, car designers focused their energies on the development and innovation of mechanical engineering. First half of the 20th century, all about the basic structure of the car has been invented, automotive designers begin from the outside to improve on modelling, and successively introduced the aerodynamics, fluid mechanics, human body engineering and industrial modelling design (industrial aesthetics), etc (1) spiritual gain -- spiritual satisfaction; Marx's interest rate determinism is based on the source and essence of interest. Marx reveals that interest is a portion of the surplus that the capitalist who lends capital is divided from the capitalist who borrows the capital, and the profit is the transformation form of the surplus value.