profit and lose These managerial accounting questions relate with effective cost assignment and optimal cash strategy tricks of a company enterprise-the appropriate mix of costs management strategies that maximizes the return on your investment and shareholders' wealth while minimizing the expense of operations, simultaneously. On the basis of introducing marginal concepts and mathematical argumentation, neoclassical has established a formal "perfect" mathematical model for the neoclassical "laissez-faire order" : general equilibrium. The price is the most important independent variable in this model, which can also be called price mechanism. The process of achieving general equilibrium is also a process of social resources guiding the flow of prices, so the price mechanism regulates the allocation of social resources. The rubber hose in the engine compartment will be used for a long time and it will be a problem for older vehicles. Once aging, gasoline can leak into the engine compartment. The air conditioning system will allow the smell of petrol to enter the car. Therefore, once the rubber tube is old, need to change promptly! The investment quantity is the decreasing function of interest rate, saving is the increment function of interest rate, and the change of interest rate depends on the equilibrium point of investment quantity and saving amount. Keynes's theory of money supply and demand decided that interest rates were a monetary factor rather than an actual factor. The "fish-type duck tail" model partially overcomes the lift of the air when the car is traveling at high speed, but it does not fundamentally solve the problem of lift of the fish. After a lot of exploration and experimentation, the designer finally found a new type of model - wedge. This type of vehicle is to tilt the body forward downward, and the back of the body is as straight as a knife, which can effectively overcome lift.