what is gross profit Dave Rosenberg, chief economist at Gluskin Sheff, said there was no real breakthrough in the bond market, and that current interest rate yields did not significantly break the mean and median levels since 2009. In terms of the purchase of intermediate products in the market, because a lot of manufacturers are generally buy goods from a handful of suppliers, it is beneficial to this a few suppliers to achieve economies of scale and reduce the cost of production. Moreover, market competition pressure between intermediate product suppliers forces suppliers to reduce production costs. In addition, when a few suppliers in the face of many intermediate products of demanders, these a few suppliers can be avoided due to the limited market demand caused by unstable, the loss that may lead to maintain a stable overall sales. In 1934, professor rei, of the center for fluid mechanics, used model cars to measure the aerodynamic drag of various bodies in wind tunnels 3. The cost of accounting earnings is listed in historical cost. Due to the current accounting practice in the enterprise asset is measured at the historical cost in, with the cost nature is the historical cost has been derived from the law of the transfer, so as to determine the income is an important factor in the cost and the historical cost.