The following income statements are provided for Li Company's last two years of operation: 2012 2013 Number of units produced and sold 3,600 3,200 Sales revenue $57,600 $51,200 Cost of goods sold 43,000 39,000 Gross margin 14,600 12,200 General, selling and administrative expenses 7,420 6,940 Net income $7,180 $5,260 Assuming that cost behavior did not change over the two year period, what is Li Company's contribution margin in 2013? $15,360 $14,860 $41,160 $18,460