Can someone show me how to do this problem? steps with explanations please

Will rate a thumb up for good response thanks so much!

The following is a table of activities associated with a project at Rafay Ishfaq's software firm in Chicago, their durations, what activities each must precede and the crash cost to reduce duration per week: Duration (weeks) 2 Activity A (start) B E F (end) 2 4 1 Precedes B, C E F F Crash Cost/ Week $380 $130 $220 $140 $420 4 Suppose that Rafay is only given 7 weeks (instead of 10) to complete the project. By how many weeks should each activity be crashed in order to meet the deadline? Assume that you can crash an activity down to 0 weeks duration. Activity Each Activity Should be Reduced BY (weeks) week(s) week(s) A B week(s) E week(s) F week(s) What is the total crashing cost? $ (Enter your response as a whole number.)