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 ±3 sigma confidence interval. The duration uncertainty-defined as pessimistic minus 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 ?
A、21 days.
B、 30 days.
C、 42 days.
D、 No statements is possible from the information given.