Tom Jacobs, an independent contractor, has agreed to build a new room on an existing house. He plans to begin work on Monday morning, June 1. The main concern is when he will complete the project, given that he works only on weekdays. The work proceeds in stages, labeled A through J, as summarized in the table in the file P15_34.xlsx. Three of these activities, wiring, plumbing, and duct work, will be done by separate independent subcontractors.
a. How long will the project take to complete, given the activity times (durations) in the table? Which are the critical activities?
b. Use a one-way data table to see how sensitive the project completion time is to the duration of activity H (hanging dry wall). Let the duration vary from 2 to 8 days in increments of 0.5 day.
c. Use a two-way data table to see how sensitive the project completion time is to the duration of activities E and F (electrical wiring and plumbing). Let the durations of each of these activities vary from 2 to 6 days in increments of 0.5 day.
d. Tom is currently subcontracting the electrical wiring, plumbing, and duct work. This explains why these three activities can be performed simultaneously. Suppose instead that Tom plans to do the first two of these by himself, and he can work on only one activity at a time—electrical wiring and then plumbing. Modify the critical path model appropriately. How much does the project completion time increase? What is the new critical path?
e. Continuing part d, where electrical wiring must be done before plumbing, suppose Tom must complete the project within a deadline of 17 days. You are given the crashing data in the file P15_34.xlsx. What should he do?
f. How difficult is it to add new activities to an existing project scheduling model? Answer this question by assuming that Tom must also install bookshelves in the room, and these can be installed only after the drywall has been hung. It typically takes 2.5 days to install the bookshelves. However, he has been instructed to make these bookshelves from a special type of wood, which must be custom ordered. He can place the order right away, and it is likely to take 10 working days to arrive. In addition, he has been instructed to install a wet bar in the room. This cannot be started until the plumbing and electrical wiring are finished, and this wet bar takes an estimated 3.5 days to finish. Find the new project completion time. Does the critical path change because of the new activities?