The inventory model is called with minimum stock and maximum stock in period ordered. The inventory carrying is considered to level stock (Low, Medium, and High). It is obvious that if the inventory carrying is less than safety stock then there is a back log. If the inventory carrying is greater than safety stock then there is an over-inventory. If the inventory is carrying is equal to safety stock, there is else medium inventory (as shown in Figure 1). Moreover, it can be known how long the over-inventory holds on without purchasing. These can be made possible by using Microsoft Excel. The formulations of calculation are shown below.