The Income Statement for Otto Construction Company Appears Below Average Total Assets Total $240,000

The income statement for Otto Construction Company appears below:
$\begin{array}{lr}\text { Net sales all credit sales } & \$ 180,000 \\\text { Cost of Goods Sold } & \underline{100,000} \\\text { Gross margin } & 80,000 \\\text { Operating expenses } & 30,000 \\\text { Interest expense } & \underline{12,000} \\\text { Net income before taxes } & 38,000 \\\text { Income tax } &\underline{9,500} \\\text { Net income } & \underline{\underline{\$ 28,500}}\end{array}$ Average total assets total $240,000.Otto's income tax rate is 25%.
What is the gross margin percentage?

A) 12.5%
B) 15.8%
C) 35.6%
D) 44.4%