Assume a year ago the U.S. Treasury bond yield curve was flat at a rate of 4% per year (with annual compounding) and you bought a 30-year U.S. Treasury bond. Today it is flat at a rate of 5% per year (with annual compounding). As of today, what rate of return did you earn on your initial investment if the bond was a 4% coupon bond? To make your current rate of return at least 6%, what coupon rate should the bond have