When using the Time-Cost Critical Path Method (CPM) Scheduling Model to "crash" a project, you know when you have arrived at the optimal solution when . a) You have found the critical path
b) You have run out of crash time
c) You no longer have a linear relationship with costs
d) You have reached the minimum total cost
e) You have run out of crash costs

a) You have found the critical path

Explanation:

The Time Cost Critical Path Method(CPM) in project management works by adding up/calculating duration of all tasks/activities in the project in order to find the longest time possible to complete the project. It is a method to estimate project duration using a flow chart that shows a network of tasks and estimated duration(start and finish times). The critical path is reached when project time is at the maximum/longest time of completion.

a) both were commissioned explorers