Answer:
For a person whose income is $90,000, the tax liability is $9,000 and the marginal tax rate is 30%.
Explanation:
total tax liability for someone earning $90,000:
$20,000 x 10% = $2,000
$40,000 x 20% = $8,000
$30,000 x 30% = $9,000
total tax liability = $19,000
A taxpayer's marginal tax rate, refers to the rate at which every additional dollar of income will be taxed.