P$11-2$ CPM diagram and determine critical path

The following information relates to a project. Predecessors indicate what activities must be completed before the activity on the left is started. Note that if there are no predecessors $($eg activities A$,$ B and C have none$)$ it means they can commence concurrently.

$\backslash$table$[[$Activity$,$Predecessors,Time $($days$)],[$A$,-,4],[$B$,-,10],[$C$,-,2],[$D$,$B$,20],[$E$,$A$,$D$,6],[$F$,$C$,12],[$G$,$E$,$F$,16]]$

Required:

$($a$)$ Draw the network diagram.

$($b$)$ List the paths in the network and identify the critical path.

$11/$Project Management

$18$ of $21$

$($c$)$ What is the total project completion time?