Es Co. produces a single product. Last year Es's net operating income under absorption costing was $3,600 lower than under variable costing. The company sold 10,000 units during the year and its variable costs were $9 per unit of which $1 was variable selling expense. If production cost was $11 per unit under absorption costing, how many units did the company produce during the year?

A. 11,200 B. 8,800 C. 8,200 D. 11,800