Determine the taxable amount of Social Security benefits for the following situations. If required, round your answers to the nearest dollar. 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 $41,000, no tax-exempt interest, and $14,350 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 $89,500, no tax-exempt interest, and $13,425 of Social Security benefits. As a result, $? of the Social Security benefits are taxable.