28 There is uncertainty regarding the duration of activities D and E in the project described in Exercise 27 expressed by the following data:

Time (weeks)

Activity Optimistic Most likely Pessimistic D 6 7 8 E 5 6 9

a. Using an early-start approach, calculate the probability of completing the project within 22 weeks or less.

b. Repeat part

(a) using a late-start approach. State your assumptions in both cases.