Jessie, an unmarried taxpayer using the single filing status, received $16,000 of Social Security retirement benefits this year. Jessie also received $5,000 of interest income and $45,000 of income from her retirement plan during the year. How much of Jessie's Social Security benefits must be included in her gross income this year?

$0.

$8,000.

$13,600.

$16,000.