PERT calculation; please help me calculate


Together with your team, you applied three-point estimation on a Critical path which consists of two activities. The following duration uncertainties are all calculated assuming a ±3sigma Confidence interval. The duration uncertainty—defined as pessimistic minus optimistic estimate—of the first activity is 18 days; the second estimate has an uncertainty of 24 days. Applying the PERT formula for paths, what is the duration uncertainty of the entire path?






 The solution for this question has been already posted in another forum