Free slack is defined as the amount of time in a schedule that can be used before the next task is delayed. On the other hand, total slack is the amount of time in a schedule that a task can be delayed before the entire project's completion date is delayed. It is essential to clearly distinguish between the two as in some instances the whole project may require to be adjusted so as to finish the project on time or by an earlier date. At other times some given phase of the project might require to be completed soon so as to begin the next phase earlier