During 2015, Maria's employer withheld $1,500 from her wages for state income taxes. She claimed the $1,500 as an itemized deduction on her 2015 federal income tax return which included $8,000 of itemized deductions. Maria is single. On her 2015 state income tax return, her state income tax was $900. As a result, Maria received a $600 refund in 2016. What amount must Maria include in income in 2016?