To keep costs at a minimum and decrease the completion time by 1-1/2 days, Networks, Inc.
should crash activity(ies):
Answer(s): A
Explanation:
The critical (longest) path is A-D-E, which has an expected time of 13 days (5.5 + 7.5). However, to decrease the project's completion time by 1.5 days, paths A-B-C-E (4.5 + 1.0 + 6.5 = 12 days) and A-B-D-E (4.5 + .5 + 7.5= 12.5 days) as well as A-D-E must also be shortened. Hence, A-D-E must be reduced by 1.5 days. A-B-C-E by .5 day, and A-B-D-E by 1.0 day. The only way to decrease A-D-E by 1.5 days is to crash activity AD (5.5 expected time - 4.0 crash time = 1.5 days). Crashing DE results in a 1.0-day saving (7.5-6.5) only. Crashing AB is the efficient way to reduce both A-B-C-E and A-B-D-E by the desired amount of time because it is part of both paths. The incremental cost of crashing AB is US $1,000 (US $4,000 crash cost - US $3,000 normal cost) to shorten the completion time by 1.0 day (4.5 - 3.5). The alternatives for decreasing both A-B-C-E and A-B-D-E are more costly.