If you would have to pay $5000 in taxes on a $25,000 taxable income and $7000 on a $30,000 taxable income, then the marginal tax rate on the additional $5000 of income is:

A. 40 percent and the average tax rate is about 23 percent at the $30,000 income level.
B. 50 percent and the average tax rate is 40 percent at the $30,000 income level.
C. 40 percent and the average tax rate is 25 percent at the $25,000 income level.
D. 30 percent but average tax rates cannot be determined from the information given.

answer: A. 40 percent and the average tax rate is about 23 percent at the $30,000 income level.