Question

Problem 5-18 The following CPM network has estimates of the normal time in weeks listed for the activities: CS 103 a. Identify the critical path. O A-C-D-E-G O A-C-D-F-G A-B-D-E-G O A-B-D-F-G b. What is the length of time to complete the project? Number of weeks c. Which activities have slack, and how much? OB, 2 week(s); F, 4 week(s). OC, 3 week(s); F. 3 week(s). OB, 2 week(s): E, 3 week(s). O C. 3 week(s); E, 3 week(s). Here is a table of normal and crash times and costs. ACTIVITY A B NORMAL CRASH NORMAL CRASH TIME TIME COST COST 7 6 $7,100 $ 8,600 6 4 5,400 9,000 3 2 8,450 10,200 5 4 2,450 4,900 3,750 4,400 5,700 9,200 4 3 4,650 7,000 G

Answer 1

Activity	ES	EF	LS	LF	Slack
A	0	7	0	7	0
B	7	13	7	13	0
C	7	10	10	13	3
D	13	18	13	18	0
E	18	25	18	25	0
F	18	22	21	25	3
G	25	29	25	29	0

Critical path is ABDEG with duration 29.

(i) Critical path is ABDEG. Option 3 is right.

(ii) Project duration is 29 weeks

(iii) C and F have slack of 3 weeks. Option 2 is right.

(iv)

Activity	Slope	Max crash
A	1500	1
B	1800	2
C	1750	1
D	2450	1
E	650	1
F	3500	1
G	2350	1

The cheapest activities on CP are E and A which can be crased for one week each.  Option 3 is right.

Total cost of crashing for 2 weeks is 2150. Critical path has not changed as the non critical activities have a slack of 3, which is less than crash duration.