Which of the following is right about slack time?
a. Slack activity time is the difference between the early start and the late finish of a project activity time.
b. In a CPM analysis if you subtract the late finish from the early start the result is the activity's slack time.
c. In a CPM analysis if you subtract the early start from the late finish the result is the activity's slack time
d. An activity's slack time on critical path of a project is greater than 0.
e. None of the above