A loan of $12,000 is being repaid with payments of $1,500 at the end of each year for 10 years. These payments can earn interest at an effective rate of 6% per annum. At the end of the year, this interest is reinvested at the annual effective rate 5% for the first 6 years and only 4% for the second 4 years. Find the yield rate over the 10-year period.