Justin Timberlake, a single taxpayer, earns $$78,200$ in taxable income and $$13,600$ in interest from an investment in City of Los Angeles bonds. $($Use the U$.$S$.$ tax rate schedule.$)$

Required:

If Justin earns an additional $$40,000$ of taxable income, what is his marginal tax rate on this income?

What is his marginal rate if$,$ instead, he had $$40,000$ of additional deductions?