A business operated at 100% of capacity during its first month, with the following results:

Line Item Description	Amount	Amount
Sales (104 units)		$520,000
Production costs (130 units):
Direct materials	$65,000
Direct labor	16,250
Variable factory overhead	29,250
Fixed factory overhead	26,000
Total production costs		$136,500
Operating expenses:
Variable operating expenses	$6,320
Fixed operating expenses	3,380
Total operating expenses		9,700

The amount of contribution margin that would be reported on the variable costing income statement is

a. $519,870

b. $425,280

c. $421,900

d. $510,300