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