A business operated at 100% of capacity during its first month, with the following results: Sales (120 units) $600,000 Production costs (150 units): Direct materials $75,000 Direct labor 18,750 Variable factory overhead 33,750 Fixed factory overhead 30,000 157,500 Operating expenses: Variable operating expenses $6,040 Fixed operating expenses 3,630 9,670 What is the amount of the contribution margin that would be reported on the variable costing income statement? a. $491,960 b. $488,330 c. $599,850 d. $590,330