A local service station is open 7 days per week, 365 days per year. Sales of 10W40 grade premium oil average 25 cans per day. Inventory holding costs are $0.90 per can per year. Ordering costs are $7 per order. Lead time is two weeks. Backorders are not practical—the motorist drives away. |
a. |
Based on these data, calculate the economic order quantity and reorder point. Hint: Assume demand is deterministic. (Round your answers to the nearest whole number.) |
Economic order quantity | cans | |
Reorder point | cans | |
b. |
The boss is concerned about this model because demand really varies. The standard deviation of demand was determined from a data sample to be 7.55 cans per day. The manager wants a 90 percent service probability. Determine a new inventory plan based on this information and the data in a. Use Qopt from a. (Use Excel's NORMSINV() function to find the correct critical value for the given ?-level. Do not round intermediate calculations. Round "z" value to 2 decimal places and final answer to the nearest whole number.) |
New reorder point |
cans |
Given are following data :
Annual demand of premium oil = D = 25 / day x 365 days = 9125 cans
Ordering cost = Co = $ 7 per order
Inventory holding cost = Ch = $0.90 per can per year
Economic order quantity ( EOQ )
= square root ( 2 x Co x D / Ch )
= square root ( 2 x 7 x 9125/ 0.90 )
= 376.75 ( 377 rounded to nearest whole number )
Demand per week = 25 cans / day x 7 days per week = 175 cans
Lead time = 2 weeks
Therefore , reorder point = Demand / week x Lead time = 175 / week x 2 weeks = 350 cans
ECONOMIC ORDER QUANTITY = 377 CANS |
REORDER POINT = 350 CANS |
Z value for 90 percent service level = NORMSINV ( 0.90 ) = 1.2815 ( 1.28 ROUNDED TO 2 DECIMAL PLACES )
Standard deviation of demand = 7.55 cans per day
Lead time ( i.e. 2 weeks ) = 14 days
Therefore , standard deviation of demand during lead time = 7.55 x Square root ( 14 ) = 7.55 x 3.741 = 28.2445
Therefore , safety stock = Z value x Standard deviation of demand during led time = 1.2815 x 28.2445 = 36.195 ( 36 rounded to nearest whole number )
Therefore , revised reorder point
= Average daily demand x Lead time ( days ) + safety stock
= 25 x 14 + 36
= 350 + 36
= 386
THE NEW INVENTORY PLAN WILL HAVE A REORDER POINT OF 386 CANS ( HAVING SAFETY STOCK OF 36 CANS) |
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