A real estate development company is planning to construct a stadium building. The estimated construction cost is $20 million. The owner is authorized to issue $23 million of bonds. The bonds will be redeemable at the end of the 30th year. The annual interest rate of the bond principal is 10% for the first 10 years, 12% for the second 10 years, and 15% for the last 10 years. The highest bid received is $22.5 million. (1) Draw the cash flow diagram. (2) Calculate the effective annual rate of interest over the 30-year bond period.