PERT/CPM network and critical path.

1) Organizers for a political convention have determined ten activities that must be done before the convention begins.

Activity Immediate Predecessors Time (Weeks)
A ---                                 10
B A                                 4
C B                                 2
D B                                 2
E A                                 6
F A, C                                 3
G D                                 4
H F, G                                 6
I D                                 5
J E                                 4


Please:
a.  Draw out the PERT/CPM network for the project.
b.  Identify the critical path.  
c.  Determine how many weeks prior to the convention the work must begin.


Thank you in advance for your insight.