$3\mathrm{.}9$ Task time estimates for the modification of an assembly line at Jim Goodale's Carbondale, Illinois, factory are as follows:

$\backslash$table$[[$ACTIVITY$,\backslash$table$[[$TIME $($IN$],[$HOURS$)]],\backslash$table$[[$IMMEDIATE$],[$PREDECESSORS$]]],[$A$,6\mathrm{.}0,-],[$B$,7\mathrm{.}2,-],[$C$,5\mathrm{.}0,$A$],[$D$,6\mathrm{.}0,$B$,$ C$],[$E$,4\mathrm{.}5,$B$,$ C$],[$F$,7\mathrm{.}7,$D$],[$G$,4\mathrm{.}0,$E$,$ F$]]$

a$)$ Draw the project network using AON $.$

b$)$ Identify the critical path.