please explain how to calculate the "d" part, please.

Development of Version 2.0 of a particular accounting software product is being considered by Jose Noguera's technology firm in Baton Rouge. The activities necessary for the completion of this project are listed in the following table: 3 1 Activity B D E F G Normal Time Crash Time Normal (weeks) (weeks) Cost 4 $2,200 2 $2,200 3 3 $600 8 4 $2,400 6 3 $800 3 2 $3,400 4 2 $1,600 Total Cost with Immediate Crashing Predecessor(s) $2,800 $2,900 $600 $2,720 A $1,175 B $4,600 $2,200 DE a) Based on the given information regarding the activities for the project, the project length = 16 weeks. b) The total cost required for completing this project on normal time = $ 13200 c) For reducing the duration of the project by one week, the activity that should be crashed first is activity D The cost of the project based on the first activity selected for crashing will increase by $ 80 d) The maximum weeks by which the project can be reduced by crashing = 7 Total cost of crashing the project to minimum (or maximum weeks possible) - $0 weeks