Problem 3: Building a backyard playground for an elementary school consists of nine major activities. The activities and their immediate predecessors are shown here: A B Activity Immediate Predecessor A, B D A, B E B F G D H D, F I E, G, H The activity time (in days) for constructing the playground project are given in the table: Optimistic Most Probable 5 Pessimistic 6 3 Activity A B 2 4 6 5 6 7 7 9 10 D E 2 4 6 2 3 F G H 5 8 10 6 8 10 I 3 4 5 (a) (b) (C) Construct the project network. What are the critical activities? What is the expected time to complete the project? What is the probability that the project can be completed in 25 days or fewer