Consider the following project:

Activity A$,$ Duration $3,$ Predecessor None

Activity B$,$ Duration $6$ days, Predecessor A

Activity C$,$ Duration $3$ days, Predecessor A

Activity D$,$ Duration $3$ days, Predecessors B$,$ C

Activity E$,$ Duration $4$ days, Predecessor D

Activity F$,$ Duration $6$ days, Predecessor D

What is the slack for activity B$?$

Question $6$Select one:

a$.$

None of these answers is correct

b$.$

$2$ days

c$.$

$6$ days

d$.$

$3$ days

e$.$

$0$ days