15. Consider the following project activity table, identifying each activity, its normal duration and cost, and expedited durations and costs: (5 marks) Activity A B C D E F Duration 3 days 5 days 4 days 5 days 7 days 4 days Normal Cost $1500 $3500 $6800 $2500 $4200 $2000 Duration 2 days 4 days 3 days 3 days 6 days 3 days Crashed Cost $2000 $5000 $7500 $6000 $5400 $2700 a. What is the cost per day to crash each of the activities? b. Assuming that only activities A, C, and E are part of the critical path, which activities should be crashed first