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 $42,600, no tax-exempt interest, and $14,910 of Social Security benefits. As a result, _______ of the Social Security benefits are taxable.

b. Assume Erwin and Eleanor have adjusted gross income of $18,600, no tax-exempt interest, and $20,460 of Social Security benefits. As a result, _______ of the Social Security benefits are taxable.

c. Assume Erwin and Eleanor have adjusted gross income of $118,000, no tax-exempt interest, and $17,700 of Social Security benefits. As a result, ________ of the Social Security benefits are taxable.