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. If these measures do not satisfy his base, Mr Trump still has the last option, which the Roman emperor and other dictators have long used in difficult times at home. That is to say, he can "swing the dog" by making external threats or launching foreign military adventures, thereby dispersing his supporters from what he and republican lawmakers have done. The new Surface Pro(2017) accounts for 9.2%, roughly the total of the Surface Book(7.5%) and the Surface Laptop (2.0%). The U.S. crude oil inventory unexpectedly fell 5.2 million barrels last week, pushing U.S. oil further higher, noted the zero hedge fund. U.S. crude stocks have declined for five consecutive weeks, while gasoline inventories have increased for five consecutive weeks. If there is a clear indication of an increase in the EIA Cushing crude inventory released on Wednesday (December 20), crude stocks could end the five consecutive decline.