For the data given in problem 8:
Average monthly sales = 120 units
Ordering cost = $25 per order
Carrying cost = 35 percent per year
Item cost = $300 per unit
Lead time = 4 days
Standard deviation of daily demand = .2 unit
Working days per year = 250
a. Design a P system for this phone with a 92 percent service level.
b. Compare the inventory investments required for the P and Q systems (from problem 8) for various values of service level.
c. Why does the P system require a higher inventory investment?