Consider the following 7 activities:

I know how to do the first part of the question, but how do you figure out b? how do you know to look-up z=1.28?

5. Consider a project having the following seven activities: Activity Immediate Predecessors Optimistic Time (weeks) 2 4 Most Likely Time (weeks) 3 4 A Pessimistic Time(weeks) 4 8 7 B 3 5 D 5 A A B B, C D E, F E 5 3 4 3 5 7 9 7 6 5 3 F G a) Using a forward and backward pass through the network, determine the expected completion time for the project and the critical path. b) What is the expected completion time required to have a 90% chance of finishing the project in 23 weeks? a