Given the following project network:

Process diagram for $15\mathrm{.}9($Algo$).$ Process begins with Task A of $5$ weeks. Then comes Task B of $6$ weeks and Task C of $7$ weeks. Task B of $6$ weeks goes on to Task D of $5$ weeks. This ends with Task F of $2$ weeks. task C of $7$ weeks goes on to Task D of $5$ weeks and Task E of $4$ weeks. Task E of $4$ weeks ends with Task F of $2$ weeks.

a$-1.$ Identify the critical path.

a$-2.$ Identify the earliest start and finish for each task.

b$.$ Calculate the slack for every project activity.