A project manager is faced with the following activities and times associated with a building construction for a cancer research facility. Each activity can be crashed at most by 2 weeks. The cost associated with each week time reduction is given below. (note: The 1st crash and 2nd crash costs are associated with the first and second time that a specific activity is crashed. So, if you crash Activity A once, the cost is $9,000, if you have to crash Activity A a second time, the cost is $9,500)

Crash Costs
Activity Immediate Predecessor Normal Time (weeks) 1st crash 2nd crash

A 3 $9,000 $9,500
B A 6 $3,500 $6,000
C А 7 $4,000 $5,000
D B 7 $4,500 $6,000
E C 5 $7,000 $7,500
F D,E 8 $10,000 $12,000
G F 2 $14,000 $16,000

What is the minimum cost to crash this project by 2 weeks?

a. $12,000
b. $9,000
c. $16,000
d. $3,500

To get the minimum cost to crash this project in 2 weeks we have to first look to crash the activity on the critical path that has the lowest cost of crashing from the first week

critical path: A-B-D-F-G = 25 weeks

After crashing Activity B by 1 week both paths become critical paths hence we need to crash activity C and D by 1 week each so that the paths can crash simultaneously within 2 weeks

therefore the overall crash cost for 2 weeks will be

crash costs of Activities : B + C + D ( 1st crashes)

= 3500 + 4000 + 4500

= $12000