The correct answer is D. All the above.
The earliest start time (ES) of a task is the earliest time that the task can start, given the start times of its predecessors. The earliest finish time (EF) of a task is the earliest time that the task can finish, given the ES of its predecessors. The latest start time (LS) of a task is the latest time that the task can start without delaying the project. The latest finish time (LF) of a task is the latest time that the task can finish without delaying the project.
The following relations hold good:
- EF = ES + D
- LS = LF – D
- LF = LS + D
The first relation states that the earliest finish time of a task is equal to the earliest start time plus the duration of the task. The second relation states that the latest start time of a task is equal to the latest finish time minus the duration of the task. The third relation states that the latest finish time of a task is equal to the latest start time plus the duration of the task.
These relations can be used to determine the earliest start time, earliest finish time, latest start time, and latest finish time of any task in a project.