The manager of a car wash received a revised price list from the vendor who supplies soap, and a promise of a shorter lead time for deliveries. Formerly the lead time was four days, but now the vendor promises a reduction of 25 percent in that time. Annual usage of soap is 4, 500 gallons. The car wash is open 360 days a year.
Assume that daily usage is normal, and that it has a standard deviation of 2 gallons per day. The ordering cost is $30 and annual carrying cost is $3 a gallon. The revised price list (cost per gallon) is shown in the following table:
|
Quality
|
Unit Price
|
|
1-399
|
$2.00
|
|
400-799
|
1.70
|
|
800+
|
1.62
|
a. What order quantity is optimal?
b. What ROP is appropriate if the acceptable risk of a stockout is 1.5 percent?