Let's analyze the image you've uploaded. It contains a network diagram often used in project management for Critical Path Method (CPM) analysis, and a series of questions related to this diagram.

Questions Breakdown:

1. Explain what is meant by the critical path ECF.
2. Find the duration of activity E.
3. Using a given formula, which is $\text{Latest Start of a given activity} = \text{Latest Start of the next activity} - \text{Duration of this activity}$, determine the duration of activity G.
4. Find possible durations for activities A and C.

Let's Address Each:

1. Critical Path ECF:

   • The critical path is the longest path in the network diagram that determines the shortest time in which the project can be completed. If any activity on the critical path is delayed, the entire project will be delayed.
   • For path ECF, you would trace the activities E, C, and F and sum their durations to understand the length of this path.

2. Duration of Activity E:

   • The duration of activity E is marked directly on the diagram, and appears to be 3 units of time.

3. Using the Formula to Determine Duration of Activity G:

   • According to the formula provided, you would need the latest start of the next activity and subtract the duration of G to determine the latest start for G. The next activity after G might depend on its successor, and you should check the diagram for this.

4. Find Possible Durations for Activities A and C:

   • Activity A's duration is given as 7, and activity C's duration is given as 3. If the question is asking for the possible variations, you would consider how changing these durations might affect the critical path or project completion time.

Calculation Breakdown:

1. For Critical Path ECF:

   • Total Duration = Duration of E + Duration of C + Duration of F.
   • This would sum the provided durations for E, C, and F.

2. For Activity G:

   • Calculate based on the provided formula.
   • If the latest start of the next activity is known, subtract the duration of G to find the latest start for G.

Would you like a more detailed step-by-step calculation of any specific part of the question?

Follow-Up Questions:

1. How does changing the duration of activity C affect the critical path ECF?
2. Can there be more than one critical path in a network diagram? If so, under what circumstances?
3. What happens to the project duration if the duration of activity G is increased?
4. How can you identify slack in activities that are not on the critical path?
5. If activity A is delayed by 2 units, how will it impact the overall project duration?

Tip:

When analyzing critical paths, always check for any other possible paths that may become critical if certain activities are delayed, as these could become bottlenecks.