To calculate the late start and late finish dates for a set of tasks, you must do:

A.
An analysis of the critical path

B.
A forwards pass

C.
A backwards pass

D.
A and B

Explanation:
Backward Pass A calculation method used to determine late start and late finish dates for activities in Critical Path Method. Subtract the duration from the late finish date of the last activitiy and add one to get the late start date. This calculation method is called as Backward Pass and this is quite opposite to Forward Pass.

Forward Pass is a calculation method used in Critical Path Method(CPM) to identify the early start date and early finish date for the activities.
Based on the relationship between current activity and preceeding/succeeding activity the PM will calculate the early start date and early finish date of the activity. The PM will do this calculation from the starting point of the activity list. This method is called as Forward Pass