finding the profit function 2. Leakage of gasoline pipe interface Gas vehicles mainly include liquefied petroleum gas vehicles (LPG vehicles or LPGV) and compressed natural gas vehicles (CNG cars or CNGV). As the name suggests, LPG cars are fueled by liquefied petroleum gas (LPG) and CNG is powered by compressed natural gas. The CO emission of gas vehicles is more than 90 percent less than the gasoline car, the hydrocarbon emission reduction is more than 70 percent, and the nitrogen and oxygen emission reduction is more than 35 percent, which is the current relatively practical low emission vehicle. Valuation bubble In November 2017, Advisor Perspectives published an article said that in addition to the improvement of fuel efficiency, petrol consumption decline is due in large part to the following factors: the ageing staff away from the workplace; The home office model is developing more and more; Social media takes the place of face-to-face communication, and travel is unnecessary. More and more young people are no longer driving their cars. And urban population growth accelerated, reducing per capita gasoline dependence. "If there is no allow most of the European Union oriented financial services agreement, the financial sector accounts for about 7% of GDP, but about 10% of tax revenue and 14% of the exports, may be affected by the special Britain will stay there," the report said. The Christmas season is an occasion you will certainly wish to spend with your friends and family. It is not even the sharing of gifts that matters, although you cannot discount the wide smiles it brings. It is the presence of people you love while you celebrate the summer season?s highlight, Christmas Eve. You should be prepared with many activities that may continue the fun in the air and steer clear of what every host or hostess fears most, which is boredom. One of the wonderful activities you can do is to get everyone sing in unison each of the Christmas songs they know.