A company’s ending inventory of finished goods has a total cost of $10,000 and consists of 500 units. If the overhead applied to these goods is $4,000, and the predetermined overhead rate is 80% of direct labor costs, how much direct materials cost was incurred in producing these 500 units?

a. $10,000

b. $ 6,000

c. $ 4,000

d. $ 5,000

e. $ 1,000