Crash Project by 4 Days: Solve Part B | Help w/ Table

[rowdy3]

By how many days should each activity be reduced the project completion time by 4 days? I have all the parts right except for part B. I thought it was 2 but it's not. What I did was subtract normal time from crash time and it worked for all the problems except B. Here's a link to the table. Any ideas?

 

[256bits]

A couple questions, or observations:
1. What is "crashing" a project? Is that the term now used to refer to speed up a project towards earlier completion? In economics, or engineering?
2. I feel that what you have done is just subtract the values in crash Time from those in Normal Time. That gave the correct answer for some cases, but apparently not for Activity B.
3. You have to take into account Immediate Predessor to see which activities are dependant upon others, and which activities can be simultaniously worked upon.
4. IF this is homework please POST in homework section

 

[Vanadium 50]

What is your critical path?

On that critical path, you have two tasks. Which one is cheaper to speed up?

When you speed that up by the maximum, you now have two parallel critical paths, with four items, but only 3 can be sped up. To advance the completion date, both paths have to be sped up.

What effect does B have on the project completion time?

 

[Drakkith]

Thread moved to HW forum. Rowdy, for future reference, please post all homework-style questions like these in the appropriate homework forum.