The information necessary to conduct a bottom-up estimate of project time and cost starts with the . Multiple Choice work package level 5 elements of the PBS milestones level 4 elements of the WBS planning horizon

The information necessary to conduct a bottom-up estimate of project time and cost starts with the work package.

Bottom-up estimate builds detailed cost and time estimates from the lowest level of detail for the work package.  This process improves the project's ability to be achieved within the estimated amounts of money and time.

The work package encompasses the required steps to complete the building blocks of the work breakdown structure and so actualize the project objectives.

In project management, the work requirements are broken down into  work packages.  Such breakdown enables various teams to simultaneously or sequentially work on the different project components.

Thus, information required for conducting a bottom-up estimate of project time and costs starts with the work package and not level 5 PBS elements or level 4 WBS elements.

Learn more about the importance of work packages in project management here:

sorry I had never done this before