Answer:
b. $800
Step-by-step explanation:
For computing the total annual inventory cost first we have to compute the economic order quantity which is shown below:


= 200 units
The total cost of ordering cost and carrying cost equals to
= Annual ordering cost + Annual carrying cost
= Annual demand ÷ Economic order quantity × ordering cost per order + Economic order quantity ÷ 2 × carrying cost per unit
= 4,000 ÷ 200 units × $20 + 200 ÷ 2 × $4
= $400 + $400
= $800
We simply applied the above formulas