15. You and several of your key team leader are really struggling with estimating the overall cost of the project. The most probable cause for this estimating difficulty can be attributed to:A. Initial poor scope definitionB. Lack of required resourcesC. Insufficient funds D. Problems with the overall schedule

The most probable cause for the difficulty in estimating the overall cost of the project can be attributed to "A. Initial poor scope definition".

Here's why:

1. Scope Definition: The scope of a project is a clear definition of what the project is supposed to achieve. This includes the project's objectives, deliverables, milestones, and tasks. If the scope is not clearly defined at the beginning of the project, it can lead to confusion and misunderstandings later on, making it difficult to estimate the overall cost.

2. Resources and Funds: While lack of resources and insufficient funds can indeed make project cost estimation difficult, these are usually consequences of a poorly defined scope. If the scope was clearly defined, the necessary resources and funds would have been taken into account in the initial cost estimation.

3. Schedule: Problems with the overall schedule can also be a result of poor scope definition. If the scope was clearly defined, the schedule would have been set accordingly, taking into account all the tasks and milestones that need to be achieved.

Therefore, while all of these factors can contribute to the difficulty in estimating the overall cost of the project, the most probable cause is initial poor scope definition.