Assume that you have the revenue data of the last 4 months, but they are not ordered (You have only the numbers but you don't know which number matchs with which month). The revenues are 8.000 , 9.000 , 11.000 $ and 15.000 . You know that the revenue in September will be the forecast with weighted average method for the last 2 months (weights are 0,40 for July and 0,60 for August). And your total costs for September will be exactly 10.000 . Assuming that the forecast with the weighted average method will be 100% accurate, what is the VaR in September with 90% confidence interval