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	$6,250
Fixed operating expenses	3,210	9,460

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

a.$559,860

b.$550,540

c.$458,550

d.$455,340