Bert is a single individual and received a salary of $29,400 before he retired in October of this year. After he retired, he received Social Security benefits of $3,200 during the year.

a. What amount, if any, of the Social Security benefits are taxable for the year?

b. Would the answer be different if Bert also had $1,600 of tax-exempt interest?

c. What if he had had $8,400 of tax-exempt interest?