In a project network (where activity times are fixed, not probabilistic), which of these is true:
1. the difference between the durations of the 'longest path' and the 'shortest path', when divided by six, gives the standard deviation of the project completion time
2. the length (duration) of the 'shortest path' is the earliest time when the project can be completed
3. the length (duration) of the 'longest path' is the earliest time when the project can be completed
4. the average of the duration of the 'shortest path' and the 'longest path' is the average project completion time