$2.$ If your earliest start is $8$ and your latest start is $10$ for the same activity in a CPM $($Critical Path Method$)$ analysis, which of the following statement holds?

A$.$ The earliest finish time must be $8$ B$.$ The slack for this activity is $2$

C$.$ The latest finish time must be $12$ D$.$ All of the above

E$.$ None of the above

$3.$ Flow time $($not the $$theoretical flow time$)$ can be defined as:

I. The time that a unit is being processed by the machines and workers in the system

II$.$ The time that a unit which leaves the process has spent within the process

III. The time for a unit to move through the system