In: Operations Management
A discount appliance store sells iPhones. The store purchases iPhones at a price of $95 per unit. The following information applies to this product.
The store operates 52 weeks per year, 6 days per week. It has a continuous inventory review system.
Suppose that the discount appliance store uses a P system instead of a Q system. They order inventory every 12 days.
a.
Unit Cost P = 95
Daily Demand d = 20 units
Annual Demand D = 20*52*6 = 6240
Ordering cost S = 56
Holding cost H = 25%*95 = 23.75
SD of daily demand = 4 units
Service Level = 90%
Z = 1.28
Lead Time L = 10 days
On hand Inventroy = 220 units
EOQ = (2DS/H)^(1/2)
EOQ = (2*6240*56/23.75)^(1/2)
EOQ = 171.54
EOQ = 172 units
Total Cost at Q = (D/Q)*S + (Q/2)*H + P*D
Total Cost (Q=172) = (6240/172)*56 + (172/2)*23.75 + 6240*95 = 596874.13
Total Cost (Q=500) = (6240/500)*56 + (500/2)*23.75 + 6240*95 = 599436.38
Saving in Cost = 599436.38 - 596874.13 = 2562.25
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Review Period = 12 days
T = d*(L + Review Period) + Z*SD of daily demand*(L+Review Period)^(1/2)
T = 20* (10+12) + 1.28*4*(10+12)^(1/2)
T = 464.01 units
T = 464 units
b.
Safety Stock with Q System = Z*SD of daily demand*(L+Review Period)^(1/2)
SSq = 1.28*4*10^(1/2)
SSq = 16.19 = 16 units
Safety Stock with P System = Z*SD of daily demand*(L+Review Period)^(1/2)
SSp = 1.28*4*(10+12)^(1/2)
SSp = 24.01
SSp = 24 units
Increase in Safety Stock = 24 - 16 = 8 units
c.
Order Quantity Q = T - On Hand Inventory
Q = 464 - 220
Q = 244 units