Task time estimates for a production line setup project at Robert Klassen's Ontario factory are follows: $(10)$

Activity Time $($in hours$)$ Immediate Predecessors

A

$6\mathrm{.}0$

B

$7\mathrm{.}2$

$5\mathrm{.}0$

$6\mathrm{.}0$

$4\mathrm{.}5$

A

B$,$ C

B$,$ C

D

E$,$ F

a$.$ Draw the network.

b$.$ Find the completion time and the activities on the critical path.

c$.$ How much slack do the activities not on the critical path have?