Question

What is the minimum cost of crashing the following project that Roger Solano manages at Slippery Rock University by 4​ days?

Normal Crash Time Normal Total Cost Activity Time (days) (days) Cost with Crashing Immediate Predecessor(s) S300 S600 $750 $1,200 $1,100 $500 $650 $1,500 $1,650 2

A)By how many days should each activity be crashed to reduce the project completion time by 4​ days? Fill in the table below. ​(Enter your responses as whole numbers.​)

B) The total cost of crashing the project by 4 days is $. (Enter your response as a whole number.)

Answer 1

(a)

Let us first look at the network diagram -

Hence, the possible network paths and their durations are -

AD --> 6+5 = 11 days
B --> 7 days
CE --> 6+4 = 10 days

Hence, the project duration is 11 days (duration of the longest path which is the critical path)

The project duration has to be crashed by 4 weeks => Required project Duration = 7 days

For path AD, A can be crashed by 1 day and D can be crashed by 3 days, bringing duration to 7 days

Path B need not be crashed

For Path CE, C can be crashed by 1 day and E can be crashed by 2 days, bringing duration to 7 days

Hence, the Activities should be crashed as below -

Activity	Each activity should be reduced by (days)
A	1
B	0
C	1
D	3
E	2

(b) Cost of crashing = cost of crashing A + Cost of crashing C + cost of crashing D + Cost of crashing E

= (1100-800) + (650-600) + (1500-750) + (1650-1200) = $1,550