In 2018, we must: Economic profits in perfect competition and monopolistic competition market has a special purpose, a positive profit can attract more enterprises to enter the market, increasing competition and push the market equilibrium price low, exclude some enterprises lack of competitiveness in the market, to achieve long-term equilibrium; On the contrary, negative economic profit can eliminate some of the original enterprises in the market, because the supply is reduced, the market equilibrium price will be pushed up, and the long-term equilibrium will be achieved. The result of the two cases is that economic profits disappear from each manufacturer and the manufacturer's total income is at the lowest point of average cost. The first wedge-shaped car was made in 1963, and the car was highly regarded as an expert in car shape design. In 1968, gm's Ozzie toronado improved and developed the wedge-shaped car, and in 1968, it was adopted by the Cadillac premium sedan, eldo. Wedges are widely used in racing cars. Because the car first considers the influence of fluid mechanics (aerodynamics) and other issues on the automobile, the body can be made entirely by wedge, while the ride comfort is considered as a secondary consideration. Like the Italian ferrari in the 1980s, it was a typical wedge shape. Wedge shape for currently considering the high-speed car, whether from the aspects of its modelling concise, move feeling, or from its embodiment of aerodynamics, are conform to the requirements of the modern people's subjective, with a strong contemporary breath, give a person with beautiful enjoyment and speed fast. Japan's Toyota motor co., the MR2, is an engine sports car (the tail is fitted with a flexible flow board) that can be called a car in a wedge car. Independence is more difficult in an age when cross-border spillovers of national monetary policy become powerful. These spillover effects make central Banks consider the impact of their policies on foreign and global systems. But it is difficult to pursue global goals when the central bank operates under the narrow, centralized mandate of its independence, and is close to impossible.