EST is the time at which the activity cannot be started earlier than this time (waiting time).
In the above network, event 4 occurs when activities A(1-2), B(1-3), C(2-4) and D (3-4) are completed. In other words, event 4 occurs when paths 1-2-3-4 and 1-3-4 are completed and the requirement of expected time for the two paths is 23 and 20 weeks, respectively. In general, the EST of an event is the duration of the longest path among the paths. In this case, 1-2-3-4 is the path with longest time (23 weeks). Therefore, the
EST for the activity F is shown in the network as:
Participants