A business operated at 100% of capacity during its first month and incurred the following costs:

Production costs (20,000 units):
Direct materials	$180,000
Direct labor	240,000
Variable factory overhead	280,000
Operating expenses:
Variable operating expenses	$130,000
Fixed operating expenses	50,000	180,000

If 1,600 units remain unsold at the end of the month, the amount of inventory that would be reported on the variable costing balance sheet is

a. $78,400

b. $66,400

c. $56,000

d. $64,000