Quick back of an envelope calculation of interest. They all offer various rates but average of the four is near 6.2% a year. BK in 2008 would be 13 years. $25 par x .062 = $1.55 interest income a year potential. 13 ( years) x 1.55 = $20.15 total interest. The interest isn’t compounding so this number is within fractions of a dollar per year what the income would be.