ID probabilistic model and safety stock Average daily demand for a product is normally distributed with a mean of 5 units and a standard deviation of 1 unit. Lead time is fixed at four days. How much more safety stock is required if the service level is raised from 80 percent to 90 percent?

		an increase of about 0.69 units
		a decrease of about 1.65 units
		an increase of about 0.90 units
		a decrease of about 2.33 units