Example: You  are given  the followings  information in regard to an item:

Annual usage     = 20,00 units.

Ordering cost     = Rs. 160 per order

 Carrying cost    = 20 % of the average inventory investment

 Unit  cost          =  Rs. 2

 Lead time         = 10 working  days

Total working  days = 250  per annum

It is  observed from  the past date that the demand during lead time has been up to  a maximum  level  of  150 unit  per day. Keeping this level  in mind what safety stock would  you recommend ? also  determine : 

a. The re order  level when the safety stock level suggested by you is kept in stock.

b. Average level of inventory stock help

c. The ordering and carrying costs associated with this fixed order inventory  policy .

Solution;

 We   know  safety stock     SS  =  max  DDLT - average DDLT

 With maximum demand per day = 150 units,

 Average demand per day = 20,000/250= 80 units

Lead time = 10 days

 We have  Maximum DDLT =  150x 10 = 1000units and

 Average DDLT = 80x 10 = 800 units

                                                 SS = 1500- 800= 700 units

1.       Re order  level           =SS  + average DDLT = 700+ 800= 1500 units

2.       Average stock level = SS +Q* / 2

        Q * =  2x 160x 20, 000/x0.20x2x = 4, 000 units

 From the  given  information            

 Thus average stock level    = 700 + 4000/ 2 = 27 00 units

3.  Ordering cost    = 20, 000/ 4000 X 160 = Rs. 800

4.  Carrying cost    = 2700x 0.40= Rs. 10 80

5.  Total cost  = 800+1080+ =Rs 18880