1. Use the Baumol-Tobin inventory model to answer the following questions: (1) When the interest rate decreases by a percentage of 6%, by what percentage does the demand for money increase or decrease? (2) Suppose a person's monthly salary is 40,000 yuan, and the company transfers it to his deposit account at the beginning of the month. The monthly interest rate of the deposit is 4%, and each withdrawal will cost $2 fee. If this person will consume all the income evenly every month, please calculate the average monthly holding currency balance of this person is How many? What is the optimal number of withdrawals from the bank per month? (3) Under (2), if the economic downturn coincides with this person's salary reduction, his monthly salary will be reduced to 30,000 yuan, and the bank will increase the withdrawal fee. It is 5 yuan each time, and the monthly deposit interest rate is reduced to 0.1%. What is the average monthly currency balance in this situation?