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Dyson specializes in repairing vacuum cleaners. Dyson receives weekly deliveries

ID: 378851 • Letter: D

Question

Dyson specializes in repairing vacuum cleaners. Dyson receives

weekly deliveries from its vacuum cleaner belt supplier, who replenishes belts up to a level

that Dyson appliance is free to specify. Dyson buys a very popular belt at a unit price of

$17.50. The annual inventory carrying charge is 20%. Weekly demand for belts is normally

distributed with mean 86 and standard deviation 24. Dyson management wants to limit

the probability of a stock-out on any given week not to exceed 1%.

(a) What replenishment level would you recommend?

(b) What is Dyson' average level of safety stock?

(c) What is Dyson annual cost of holding cycle stock?

Explanation / Answer

Since probability of stockout not to exceed 1%, service level = 99% ( 0.99)

Corresponding Z value for probability 0.99 = NORMSINV ( 0.99) = 2.326

Given. Lead time of delivery ( Dyson receives weekly delivery ) = 1 week

Mean Weekly demand = m = 86

Standard deviation of weekly demand = Standard deviation of demand during lead time = S = 24

Thus average safety stock = ZxS = 2.326 x 24 = 55.82 ( 56 rounded to nearest whole number )

Thus , Replenishment stock = Mean weekly demand x Lead time ( weeks) + Safety stock

                                                 = 86 x 1 + 56

                                                   = 86 + 56

                                                    = 142

Given above replenishment quantity,

Cycle stock will fluctuate at steady rate between 86 and 0. Thus average cycle stock = 86/2 = 43

Annual Unit inventory holding cost = 20% of $17.50 = $3.5

Thus, Dyson’s annual cost of holding cycle stock

= Annual unit inventory holding cost x Cycle stock

= 3.5 x 43

= $150.5

REPLENISHMENT LEVEL = 142 VACUUM CLEANER

AVERAGE LEVEL OF SAFETY STOCK = 56 VACUUM CLEANER

ANNUAL COST OF HOLDING CYCLE STOCK = $150.5

REPLENISHMENT LEVEL = 142 VACUUM CLEANER

AVERAGE LEVEL OF SAFETY STOCK = 56 VACUUM CLEANER

ANNUAL COST OF HOLDING CYCLE STOCK = $150.5