The following is a question possibly involving "Exponential probability distribution", "Gamma Function", and/or "Gamma probability distribution".

Weekly demand at a grocery store for a brand of breakfast cereal is Normally distributed with a mean of 300 boxes and a standard deviation of 75 boxes. The store orders cereal from a distributor weekly. How many boxes should the store order for a week to have only a 2.5 percent chance of running short of this brand of cereal during the week