Keith Littlefield is a racecar driver on the NASCAR circuit. He has promised to participate in the Pocono 300, to be held 15 weeks from now. In order to be competitive, Keith feels he must completely...

Keith Littlefield is a racecar driver on the NASCAR circuit. He has promised to participate in the Pocono 300, to be held 15 weeks from now. In order to be competitive, Keith feels he must completely modify his racecar. The following activity chart summarizes the normal crash costs and completion times of the rebuilding project activities

a. Determine the minimal time it will take to modify the racecar if no activities are crashed.

 b. Which activities should be crashed and by what amount to meet the 15-week target date? What are the total costs of the modifications if the deadline is met?