Campbell, a single taxpayer, earns $450,000 in taxable income and $3,000 in interes (Use the U.S. tax rate schedule). Required: a. If Campbell earns an additional $17,500 of taxable income, what is her marginal ta b. What is her marginal rate if, instead, she had $17,500 of additional deductions? (For all requirements, do not round intermediate calculations.) . % Marginal tax rate Marginal tax rate b. :%