Scot and Vidia, married taxpayers, earn $240,400 in taxable income and $5,000 in interest from an investment in City of Tampa bonds. (Use the U.S. tax rate schedule for married filing jointly). Required: a. If Scot and Vidia earn an additional $80,400 of taxable income, what is their marginal tax rate on this income? b. What is their marginal tax rate if, instead, they report an additional $80,400 in deductions?