The manager would benchmark the planned time with other similar projects completed. In case historical data is not available, the project manager would evaluate the probabilities associated with each activity duration to arrive at the "Most Likely", "Optimistic", and "Pessimistic" project durations.
The advantage of network is that the interdependencies between various activities are captured effectively. CPA allows the project manager to focus on the critical activities and allocate resources efficiently, and helps deciding which activities to "crash". Its disadvantage is that it is complex, and unlike other planning tools like Gantt chart is not easily interpreted by everybody.
A work package is a subset of a project that can be assigned to a specific party for execution (Work Package 2009). Such work packages are identified as sub-levels of the WBS. For example, Colin can entrust the Level 1 activity of obtaining bank loan to a family member, who can execute this work package a separate sub-project.
The analysis is important as it allows the project manager to plan, monitor and control the project. It also forms as an important Management Information System (MIS) tool for the senior management. The analysis also allows estimation and allocation of scarce resources.