Campbell, a single taxpayer, earns $400,000 in taxable income and $2,000 in interest from an investment in State of New York bonds. (Use the U.S. tax rate schedule). Required: a. If Campbell earns an additional $15,000 of taxable income, what is her marginal tax rate on this income? b. What is her marginal rate if, instead, she had $15,000 of additional deductions? Note: For all requirements, do not round intermediate calculations. Round percentage answers to whole percent. a. Marginal tax rate % b. Marginal tax rate %