Margo has $ 2,100 withheld from her wages fro sate income taxes during 2015. In March of 2015, she paid $ 300 in additional taxes for her 2014 state tax return when it was filed in 2015. Her state income tax liability for 2015 is $ 2,500 and she pays the additional $ 400 when she files her 2015 state tax return in April of 2016. What amount should Margo deduct as an itemized deduction for state income taxes on her 2015 federal income tax return, assuming she elects to deduct state and local income taxes?

a. $ 2,100

b. $ 2,400

c. $ 2,500

d. $ 2,800

e. None of the above