please use 2020 tax rate schedule

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? (For all requirements, do not round intermediate calculations. Round percentage answers to whole percent.) a Marginal tax rate Marginal tax rate b. %