20 A series of activities must be completed in a coordinated fashion to complete a landscaping overhaul.

The following table shows the activities; their optimistic, most likely, and pessimistic durations; and their immediate predecessors.

ACTIVITY DAYS IMMEDIATE a m b PREDECESSORS A 4 8 12 —

B 4 10 13 A C 7 14 18 B D 9 16 20 B E 6 9 12 B F 2 4 6 D, E G 4 7 13 C, F H 3 5 7 G I 2 3 4 G, H

(a) Determine the expected times and variances for each activity.

(b) Construct a project network for this problem.

(c) Determine the EST, EFT, LST, LFT, and slack for each activity. Also determine the critical path and project completion time.

(d) What is the probability that the project will be finished in less than 57 days?

(e) What is the probability that the project will need at least 50 days?