The correct answer is A. $200.
The annual relevant ordering cost is calculated by multiplying the number of orders per year by the relevant ordering cost per order. The number of orders per year is equal to the demand divided by the order quantity. In this case, the demand is 18000 units and the order quantity is 1500 units. Therefore, the number of orders per year is 18000/1500 = 12.
The relevant ordering cost per order is $150. Therefore, the annual relevant ordering cost is 12*$150 = $200.
Option B is incorrect because it is the annual relevant ordering cost if the order quantity is 1000 units.
Option C is incorrect because it is the annual relevant ordering cost if the demand is 12000 units.
Option D is incorrect because it is the annual relevant ordering cost if the relevant ordering cost per order is $100.