Compute the taxable Social Security benefits in each of the following situations:
a. Erwin and Eleanor are married and file a joint tax return. They have adjusted gross income of $46,000, no tax-exempt interest, and $12,400 of Social Security benefits.
b. Erwin and Eleanor have adjusted gross income of $12,000, no tax-exempt interest, and $16,000 of Social Security benefits.
c. Erwin and Eleanor have adjusted gross income of $85,000, no tax-exempt interest, and $15,000 of Social Security benefits.