Consider the following project information: Activity A depends on nothing and has an expected time of 8 days, B depends on A with an expected time of 3 days, C depends on nothing with an expected time of 9 days, D depends on A with an expected time of 6 days, finally, activity E depends on B, C, and D and its expected time is 4 days. The slack time for activity D is

Select one:

a. 2

b. 0

c. 5

d. 4

e. 3