b) Four years ago, Valero issued $4 million worth of debenture bonds having a bond interest rate of 8% per year, payable semiannually. Market interest rates dropped and the company called the bonds (i.e., paid them off in advance) at a 8% premium on the face value. What semiannual rate of return did an investor make who purchased one $4000 bond 4 years ago and held it until it was called 4 years later?