Determine the taxable amount of social security benefits for the following situations.

a. Erwin and Eleanor are married and file a joint tax return. They have adjusted gross income of $39,200, no tax-exempt interest, and $13,720 of Social Security benefits. As a result, $ of the Social Security benefits are taxable.

b. Assume Erwin and Eleanor have adjusted gross income of $19,800, no tax-exempt interest, and $21,780 of Social Security benefits. As a result, $ of the Social Security benefits are taxable.

c. Assume Erwin and Eleanor have adjusted gross income of $116,500, no tax-exempt interest, and $17,475 of Social Security benefits. As a result, $ of the Social Security benefits are taxable.