Rolling planning laws is according to the principle of "almost fine far" a certain period of the plan, then according to the plan implementation and environmental changes and adjustments and changes to the plans for the future, and by backward, combine short-term and medium-term plans of a kind of planning method. Commercial vehicles are divided into three categories: passenger cars, vans and semi-trailer tractors. The passenger bus subdivided into small passenger car, city bus, coach, tourist bus, hinged passenger bus, coach, off-road bus, private bus. Goods vehicles are subdivided into general goods vehicles, multi-purpose lorries, full trailer tractors, off-road trucks, special operations vehicles and special goods vehicles. Security is very important, reduce risk is big potential! It is not obvious in some analyses, but it is important to note that economic profits include opportunity costs. The profit of an entrepreneur (normal profit) is usually positive, but economic profit can be either positive or negative (loss). That's why the opportunity cost is included: in a completely competitive market, when marginal cost equals marginal revenue, profit maximization or loss minimization conditions arise. If the market price is lower than the total average cost, which means that the economic profit is negative, the entrepreneur needs to compare the value of the loss and the average variable cost. If the business continues to operate, the negative economic profit must not be lower than the average variable cost, otherwise the entrepreneur would rather shut down the company than continue to take the loss. Larger suppliers can borrow cheaply from the government's regular contributions, which means they have little incentive to raise savings rates to attract customers' deposits and then lend. In the week ended Dec. 15, U.S. crude stocks fell 520 barrels to 438.7 million barrels, the API said, with analysts predicting a decrease of 3518,000 barrels. Cushing's crude inventories rose by 70,000 barrels.