education for profit The optimal combination of benefits and risks is the best combination of benefits and risks. If the benefit is certain, the risk is minimized; (1) spiritual gain -- spiritual satisfaction; In the early 20th century, famous American economist elvin fisher developed the theory of economic gain. In its book "the nature of capital and yield", first, the concept of yield is analyzed in terms of the performance of earnings, and three different types of benefits are proposed: Thus, surplus value is the intrinsic essence of profit, and profit is the phenomenon form of surplus value. Surplus value into profit, the profit and then into average profit, etc., hierarchy, the more the more escalated from abstract to concrete, it is close to the reality of capitalist society and the consciousness of the capital relationship between the parties; As a result, capital relations are becoming more and more mysterious as they leave their own source or base and get further and further away. Bourgeois economists for capitalism exploitation system, trying to deny the existence of the surplus value, no conflict between capital and employment, the product of the profit as capital itself, as the result of both production and circulation process. The so-called trinity formula of profit (interest), labor wage and land rent is the most explicit and typical defense argument of bourgeois vulgar economy. Marx's theory of profit is the transformation form of surplus value, profoundly reveals the essence and source of the profit, and profit further transformation of various concrete form again and they reflect the complexity of the capitalist production relations and class performance, thus for the proletariat and working people struggle against the bourgeoisie, and fight for the liberation of revolution provides the theory of sharp weapons. The principle of rational investment: investment in securities investment in analysis and comparison. Including ambulances, fire engines, sanitation vehicles, TV and radio cars, airport operations, municipal construction projects, etc.