Sienna faces a marginal tax rate of 25%, an average tax rate of 17.5%, and an effective tax rate of 16.8%. Sienna is considering investing in State of Arizona bonds (which pay a 5% return) or other corporate bonds (which pay an 8% return). What is Sienna's after-tax rate of return on the Arizona bonds (omit the % sign)? 20 What is Sienna's after-tax rate of return on the corporate bonds (omit the % sign)? 17