The annual holding cost as a percentage is 20%, cost per order is $50 and annual demand is 9000 units. The supplier offers the following quantity discount: 1-999 units, the unit cost is $10, 1000-1499, the units cost is $9.9, 1500-1999 units, the unit cost is $9.8, 2000 units and more, the unit cost is $9.7. The economic quantity discount when unit cost is $9.7 is approximately:

a.

687

b.

681

c.

675

d.

690

e.

693