The professor gives the answers but I need to learn the steps to get the answer

Ch. 13: Inventory Management store sells four cases of bolts each day. Order costs are $8.00 per order, and bolts costs $3.20 per case. Orders arrive three days from the time they are placed. Daily holding costs are equal to five percent of the cost of the bolts. I.At what point should he reorder bolts? [12 cases remaining) 2. For the current order quantity of 16 cases of bolts, what would be the daily total inventory costs, EXCLUDING the cost of the bolts? [$3.28] 3. What is the economic order quantity for ordering bolts? [20] 4. How much money would be saved by using the EOQ instead of the current order quantity of 16? ISO_08/day1