01 January Beginning inventory 0 Units produced 500 Units sold 400 Ending inventory 100 Excerpt from Wallis Corporation Per Unit Per Month Selling price $ 100 Direct materials 30 Direct labor 20 Variable manufacturing overhead 10 Variable selling and administrative expenses 7 Fixed manufacturing overhead $ 10,000 Fixed selling and administrative expenses 3,000 What is the company's contribution margin for January?

A. $24,000
B. $30,000
C. $32,000
D. $40,000