Mark Achins sells 3,600 electronic motors each year. The cost of these is $200 each, and demand is consistent throughout the year. The cost of placing an order is $40. While the holding cost is $20 per unit per year. There are 360 working days per year, and the lead time is 5 days. If Mark orders 400 units each time he placed an order, what would his average inventory be (in units)?

A. 100

B. 120

C. 200

D. None of the above