Variability in Transit Time

You have to select a transportation carrier to use for replenishing your inventory. Demand for the item is distributed Normally with a mean of $500$ units and a standard deviation of $100$ units per week. The cost of the item to include delivery is $$450.$ You want a CSL of $95\%.$

Option $1$: Delivery leadtime mean$=4$ weeks, StdDev $=1$ week

Option $2$: Delivery leadtime mean$=4$ weeks, StdDev $=0\mathrm{.}5$ week

Option $3$: Delivery leadtime mean$=3$ weeks, StdDev $=1$ week