please solve the following

2) A simple network has five activities, A, B, C, D and E. A is an immediate predecessor of B and of C. B is an immediate predecessor of E. C is an immediate predecessor of D. The activity durations are A = 10, B = 3, C=6, D = 2 and E=3. a) The critical path is A-B-E, duration 16. b) The critical path is A-B-C, duration 19. c) The critical path is A-B-D, duration 15. d) The critical path is A-C-D, duration 18. e) The network has no critical path 5) What is the slack on an activity that has ES = 32, EF = 40, LS = 55 and LF = 63? a) 15 b) 23 c) 31 d) 8 e) Cannot be determined I 6) A vending machine has constant service of 20 seconds per product and customers arrive at a mean rate of 2 per minute. What is the average number of customers waiting in line? a) 0.056 b) 1.33 c) 0.0056 d) 0.33 e) 0.67