In 1934, professor rei, of the center for fluid mechanics, used model cars to measure the aerodynamic drag of various bodies in wind tunnels According to the length, there are mini passenger cars (no more than 3.5 meters), small passenger cars (3.5-7 meters), medium-sized buses (7-10 meters) and large passenger cars (more than 10 meters). 4. The determination of accounting earnings shall follow the principle of revenue confirmation. The current accounting practice and the law's view of earnings are still: only after the relevant conditions of the asset value increase are met, the benefits can be generated. Income and appreciation must be measured objectively, determined or unalterable, and must be verified through some business or accounting matters. In other words, the determination of accounting income should be based on the following two principles: the realization principle of income determination and the prudent principle of income determination. According to the realization principle of revenue recognition, the enterprise income should be divided into operating income and profit and loss. The determination of operating earnings must happen in selling goods or services and other key issues, and the profit and loss refers to the production of the assets held realized gains and losses, unrealized gains and losses caused by price change is not confirmed. According to the principle of steady earnings determine when a has a variety of economic business accounting methods for when the choice, should choose the most don't overestimate the method of income, it should not be overestimated revenues and should not be underestimated cost two aspects. But even at its lowest point, interest rates were just 0.18 percentage points higher, not a quarter-point rise in interest rates. Microsoft's Surface Pro, Surface Laptop, Surface Book and Surface Studio are the main products of Microsoft's Surface series, but there is a clear difference in the share of the devices. The Surface Pro products account for the highest share (79.9%), the Surface Book (7.5%), Surface Laptop (2.0%), and Surface Studio (0.2%). In 1946, the famous British economist J.R. hicks, in value and capital, developed the concept of income into a general concept of economic gain. He argues that the real purpose of computing revenues is to make people aware of the amount of money they can spend without making them poorer. Accordingly, he gave a generally accepted definition of "the maximum amount of consumption that a person can spend at the end of the term, at the same level of prosperity". Hicks's definition, though primarily for personal gain, applies to businesses as well. In the case of the enterprise, according to this definition, the enterprise income can be understood as the maximum amount that can be allocated in the enterprise cost accounting period under the same amount of capital at the end of the term and the beginning of the period.