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?
a. $0.
b. $5,280.
c. $10,890.
d. $3,080.
e. $11,000.