Tax Rates. Based on the amounts of taxable income below, compute the federal income tax payable in 2015 on each amount assuming the taxpayers are married filing a joint return. Also, for each amount of taxable income, compute the average tax rate and the marginal tax rate.
a. Taxable income of $30,000.
b. Taxable income of $100,000.
c. Taxable income of $375,000.
d. Taxable income of $600,000.