Chuck, a single taxpayer, earns $80,750 in taxable income and $30,750 in interest from an investment in City of Heflin bonds. (Use the U.S. tax rate schedule.) (Do not round intermediate calculations. Round your answers to 2 decimal places.) a. If Chuck earns an additional S64,500 of taxable income, what is his marginal tax rate on this income? Marginal tax rate b. What is his marginal rate if, instead, he had S64,500 of additional deductions? Marginal tax rate