when a firm is maximizing profit it will necessarily be Modern economy, the interest rate as the price of money, not only restricted by many factors in the economic and social, and changes in interest rates to have a great impact on the economy as a whole, as a result, modern economists are studying the interest rate decision problem, pay special attention to the relationship between the variables and the balance of the economy as a whole, the interest rate decision theory has experienced the classical interest rate theory, Keynes's interest theory, interest rate in loanable funds theory and is-lm analysis as well as the contemporary evolution of dynamic interest rate model, the development process. 2. Accounting earnings are based on the assumption of accounting instalments, which refers to the production and operation results of a certain period of time. Early accounting earnings is calculated according to the cash basis, and the modern accounting earnings is according to the classification current income and expenses of accrual basis, after the appropriate ratio calculated. However, the benefits of cash determination are more acceptable to users.