Rebecca and Gregory, a married couple filing a joint return, reported adjusted gross income of $70,000 and

Question:

Rebecca and Gregory, a married couple filing a joint return, reported adjusted gross income of $70,000 and total allowable itemized deductions of $12,800, including$3,100 for state income taxes, in 2016. They received a $900 refund of state income taxes in April 2017. How much of the state income tax refund must be included in their income and in which year do they include it?