On August 1 of the current year, an unmarried taxpayer retires and begins receiving monthly pension checks in the amount of $2,200. During her working years, the taxpayer contributed $5,720 to her employer's pension plan with after-tax dollars. Using the taxpayer's age at the time the payments begin, the taxpayer's number of expected monthly payments is 260. Of the $11,000 in pension benefits the taxpayer received during the current year, what amount must she include in gross income?