An electronics firm uses 600 cases of transistors each....

[startingover]

An electronics firm uses 600 cases of transistors each year. The cost of storing one case for a year is 90 cents, and the ordering fee is $30 per shipment. How many cases should the firm order each time to keep total cost at a minimum, assuming the transistors are used at a constant rate throughout the year and that each shipment arrives just as the preceding shipment has been used up?

Total Cost = storage cost + ordering cost + purchase cost

Ordering cost = (Ordering cost per shipment)(# of cases in shipment)
OC = ($30)(600) = 18000

Purchasing Cost = (total of cases ordered)(cost per case)
PC = (600)(x)
PC = 600x
x = cost per case

Storage Cost = (average # of cases stored)(storage cost per case)
SC = y(.90) = .90y
y = average number of cases stored

TC = .90y + 18000 + 600x


I am even getting close?