Can some one please help me this? Here is the question:

Together with your team, you applied three-point estimation on a critical path with constist of two activites.

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 formual for the paths, what is the duration uncertainty of the entire path?

A. 21 days

B. 30 days

C. 42 days