Question

4. Environment Recycling, Inc. must clean up a large automobile tire dump under a state environmental cleanup contract. Some of the activities can be crashed. The tasks, durations (in days), costs, predecessor relationships, the crash times, and costs associated with performing the activities at their original (normal) times and for the crash times are shown as follows:

Activity	Immediate Predecessor	Normal Time (days)	Normal Cost ($)	Crash Time	Crash Cost ($)
A	--	6	1,000	5	1,200
B	--	4	800	2	2,000
C	A, B	3	600	2	900
D	B	2	1,500	1	2,000
E	C, D	6	900	4	1,200
F	E	3	1,300	1	1,400
G	E	4	900	4	900
H	G	4	500	2	900

a. Find the total project completion time. (Show all work including finding the critical path).

b. Find the lowest cost solution if the state wants to complete the project two days early. State which activities need to be crashed and calculate the crashing cost for the total project.

Answer 1

(a) Total Project Completion time = 23 weeks

(b) Crash Activity E by 2 weeks.

Crashing cost = $ 300