The following income statements are provided for Li Company's last two years of operation: 2012 2013 Number of units produced and sold 4,500 4,100 Sales revenue $69,750 $63,550 Cost of goods sold 41,700 38,000 Gross margin 28,050 25,550 General, selling and administrative expenses 17,500 16,300 Net income $10,550 $9,250 Assuming that cost behavior did not change over the two year period, what is Li Company's contribution margin in 2013? $12,825 $17,325 $13,325 $43,250

how do I get 13 325 that is the correct one I need the steps