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.

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