Mark Achin Sells 3,600 Electric Motors Each Year

Mark Achin sells 3,600 electric motors each year.The cost of these is $200 each,and demand is constant 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 200 units each time he places an order,what would his average inventory be (in units) ?

A) 100
B) 200
C) 60
D) 120
E) None of the above