A workbreakdown structure $($WBS$)$ has been completed. The project team is now collecting estimated duration times so that a schedule can be created. To estimate each activity several people who are responsible for completing the activity in the project are asked for time estimate. But as the team collects these estimated time they find considerable variance for one person's estimate to another's. Some have been more ambitious than others in determining what needs to be done. which additional document would help clarify the situation. a$.$ risk breakdown structure b$.$ schedule c$.$ scope statement d$.$ business case