Campbella single taxpayer, earns $295,000 in taxable income and $6,400 in interest from an investment in State of New York bonds (Use the U.S. tax rate schedule). Required: o. If Campbell earns an additional $20,500 of taxable income, what is her marginal tax rate on this income? b. What is her marginal rate if, instead, she had $20,500 of additional deductions