3. [Extra Credit] Consider the network diagram in Figure 1 below. B A D Figure 1: Precedence Diagram for Problem 3. The optimistic, most likely, and pessimistic durations for each activity in weeks are as follows. Activity Optimistic Most Likely Pessimistic A 2 5 8 B 3 3 4 C 1 3 2 5 3 6 a. Using the PERT chart method learned in class, calculate the expected duration and the variance of the duration for each activity.