3. Dr. Denton Fender has the following activity-on node (AON) precedence network for a small car repair project:

She has come up with the following estimates:
Duration [Wks)
Task Optimistic Most Likely Pessimistic

a. According to the classic PERT model, what is the minimum project makespan that has at least a 90 percent chance of occumng?

b. Assume that the formula for computing the standard deviation of any task j (9)is modified to the following:
where to = optimistic time, and $ = pessimistic time.
Using this modified formula for estimating the standard deviation of task duration, what is the probability that the project will be completed within 26 weeks (based on the classic PERT model)?