Alex and Mary, both under 65, file a joint tax return for 2013. Their adjusted gross income is $55,100. This total includes $4,000 of long-term capital gain from stock that had been held 3 years and 2 months prior to its sale in July. Alex and Mary claim the standard deduction and two personal exemptions. Their total income tax liability for 2013 is A. $3,773 B. $3,973 C. $4,373 D. $4,573