Forward Pass Computation

Add activity times along each path in the network $($ES $+$ Duration $=$ EF$).$

Carry the early finish $($EF$)$ to the next activity where it becomes its early start $($ES$)$ unless...

The next succeeding activity is a merge activity, in which case the largest early finish $($EF$)$ number of all its immediate predecessor activities is selected. Backward Pass Computation

Subtract activity times along each path starting with the project end activity $($LF $-$ Duration $=$ LS$).$

Carry the late start $($LS$)$ to the next preceding activity where it becomes its late finish $($LF$)$ unless...

The next succeeding activity is a burst activity, in which case the smallest late start $($LS$)$ number of all its immediate successor activities is selected.

Total Slack $)=(SL$ or $)=(SL$

Free Slack $($FS$)=$ Is the amount of time an activity can be delayed without delaying any immediately following $($successor$)$ activity.