Myrna and Geoffrey filed a joint tax return in 2014. Their AGI was $85,000, and itemized deductions were $13,700, which included $4,000 in state income tax. In 2015, they received a $1,800 refund of the state income taxes they paid in 2014. The standard deduction for married filing jointly in 2014 was $12,400.
Under the tax benefit rule, what amount of the state income tax refund is included in gross income in 2015?