this activity can start as early as time 0 or as late as time 5 (see Figure 6.45).
However, because its F F = 2 days, starting B anywhere between time 0 and time 2 will have no
effect on the succeeding activities E and F. If, however, activity B must start at time 2 + d ($5),
then the start times of the immediately succeeding activities E and F must be pushed forward
past their earliest start time (= 8) by at least d. In this manner, the precedence relationship
between B and its successors E and F is preserved