A table such as the one presented below is helpful in analysis. We begin with network having normal completion time schedule of 15 days. Critical path using normal task completion times is marked. If project is to be shortened, a task on critical path must be crashed since critical path is longest path through network. As project duration is reduced other paths may also become critical.
G is at minimum time.
Project duration cannot be further reduced since all tasks on critical path BEG are at their minimum time. Hence, this project has a minimum crash duration of 11 days. This implies 1. search for optimal project duration can cease when decrease in project duration leads to total cost increase. Mean activity completion times are noted on arcs. Sum of expected mean completion times for activities on critical path.