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 $42,800, no tax-exempt interest, and $14,980 of Social Security benefits. As a result, $___________ of the Social Security benefits are taxable.

c. Assume Erwin and Eleanor have adjusted gross income of $91,000, no tax-exempt interest, and $13,650 of Social Security benefits. As a result, $________ of the Social Security benefits are taxable.