who can solve this inventory problem?

Question

The purchasing manager for a firm is trying to determine what the safety stock should be for a particular product. She has developed the following table, which gives the distribution of demand during the lead-time and the probabilities:

Demand during lead time / probability
40/ 0.2
50/ 0.25
60/ 0.25
70/ 0.2
80/ 0.1
The carrying cost is $5 per unit per year, the ordering cost is $30 per order, and the stockout cost is $40 per unit. The reorder point is 60 units, and 6 orders are placed each year. What level of safety stock should be maintained?
ROP (reroder point)=d (daily demand) x L (order lead time) +SS (safety stock)
I don't know how to solve it.

Answer 1

the question is flawed!
the demand during lead time is meaningless, how can you know what your demand during lead time is if you don't know what your lead time is.

if your weekly demand is 10 units and your leadtime is 2 weeks then you MUST have 30 units on hand.
Which would make your safety stock 20 units.

This is not a math problem!
it is a logic problem.
I like to keep 1.5 of the lead time stock on hand as suppliers can't always be counted on to keep the lead time.