A business operated at 100% of capacity during its first month, with the following results: Sales (112 units) $560,000 Production costs (140 units): Direct materials $70,000 Direct labor 17,500 Variable factory overhead 31,500 Fixed factory overhead 28,000 147,000 Operating expenses: Variable operating expenses $5,090 Fixed operating expenses 4,090 9,180 What is the amount of the contribution margin that would be reported on the variable costing income statement? a. $550,820 b. $459,710 c. $559,860 d. $455,620