Suppose a supplier offers an incremental quantity discount for a product. The supplier charges $10 per unit for the first 2,000 units in an order, $9 per unit for the next 2,000 units, and $7 per unit for any additional units in the order. What is the average cost per unit of an order of 3,000 units? Find the closest value.
a) $7.00
b) $8.50
c) $9.00
d) $9.67