Consider the following activity list and PERT three-estimates for activity durations. (Durations are in weeks). Activity Optimistic Most likely Pessimistic Immediate estimate (o) estimate (m) estimate (p) predecessor(s) A N 3 10 B 2 3 16 C 2 15 A D N 9 A, B m W 5.5 17 B 4 13 D, E a. Find the estimate of the mean and variance of the duration of each activity. (5 marks) b. Construct the project network for this project. (5 marks) c. Find the earliest and latest start time and finish time for each activity based on the mean duration for each activity. (8 marks) d. Find the mean critical path. (2 marks) e. Find the approximate probability of completing the project within 20 weeks. (2 marks)