Determine the taxable amount of social security benefits for the following taxpayers. If an amount is zero, enter "$0".

a. Erwin and Eleanor are married and file a joint tax return. They have adjusted gross income of $34,800, no tax-exempt interest, and $12,180 of Social Security benefits. As a result, $ ____________ of the Social Security benefits are taxable.

b. Assume Erwin and Eleanor have adjusted gross income of $18,000, no tax-exempt interest, and $19,800 of Social Security benefits. As a result, $________________ of the Social Security benefits are taxable.

c. Assume Erwin and Eleanor have adjusted gross income of $81,500, no tax-exempt interest, and $12,225 of Social Security benefits. As a result, $_____________ of the Social Security benefits are taxable.