Chuck, a single taxpayer, earns $78,600 in taxable income and $10,000 in interest from an investment in City of Heflin bonds. (Use the U.S. tax rate schedule.) Required: a. If Chuck earns an additional $40,440 of taxable income, what is his marginal tax rate on this income? b. What is his marginal rate if, instead, he had $40,440 of additional deductions? (For all requirements, do not round intermediate calculations. Round percentage answers to 2 decimal places.) a. Marginal tax rate b. Marginal tax rate % %