Campbell, a single taxpayer, earns $267000 in taxable income and $4,800 in interest from an (Use the U.S. tax rate schedule) nvestment in State of New York bonds Required: a. If Campbell earns an additional $18,500 of taxable income. what is her marginal tax rate on this income? b. What is her marginal rate if, instead, she had $18,500 of additional deductions? (For all requirements, do not round intermediate calculations) a Marginal tax rate b Marginal tax rate