Order Quantity-Cycle Inventory-Safety Inventory

Question

Consider the following data pertaining to a distribution center.

Ordering cost: $50 /order
Holding cost: $4 /unit /week.
Cycle service level: 97%

Summary:

The question is related to cost accounting in finance. It deals with measures such as Order Quantity, Cycle Inventory, Safety Inventory, Reorder Level, Annual Inventory Holding, Annual Ordering Cost, etc. All these measures are calculated according to given cost and time.

Answer 1

Consider the following data pertaining to a distribution center.

Mean Weekly Demand(d): 100
Standard Deviation  of Weekly Demand(Sd): 30
Lead Time(L): 2 Weeks
No. of weeks in year: 50

Ordering cost (Cp): $50 /order
Holding cost (Ch): $4 /unit /week.
Cycle service level: 97%  
Z – value for service level 97 % = 1.89
Annual demand (D) = d * No. of weeks = 100 * 50 = 5000 units
Standard deviation of weekly demand during lead time =SL = sqrt( sum of squares of ‘Sd’ during the ‘L’ number of weeks) = sqrt( 30² + 30²) = 42.42 units

Order Quantity = Q = sqrt( (2 * D * Cp)/Ch) 
              = sqrt((2* 5000 * 50)/4)
              = 353.55 units
              =354 units approx

Cycle inventory = Q/2 
    = 353.55/2 
    = 176.775 units
    = 177 units approx

Safety inventory = z* SL 
     = 1.89 * 42.42 
    = 80.18 units
    = 80 units approx

Re-Order Level = d*L + z* SL
     = 100*2 + 1.89*42.42
    = 280 units approx

Annual Inv Holding Cost = (Q/2)*Ch
      = 353.55/2 * 4
      = $ 707 approx

number of orders per year
= D/Q
= 5000/353.55
=14.14

Annual ordering cost = (D/Q) * Cp
              = 5000/353.55 * 50
              =$ 707 approx