a)

b)

The critical path for the network activities shown below is with duration Q-X-Z; 5 months Q-Z; 4 months P-X-Z; 9 months Q-P-Y-X-Z; 17 months Q-Y-Z; 10 months P-Y-Z; 14 months The critical path for the network activities shown below is with duration C-E; 12 weeks A-B-D; 10 weeks A-B-C-D-E; 22 weeks A-B-E; 11 weeks A-D-E; 13 weeks