4. Environment Recycling, Inc. must clean up a large automobile tire dump under a state environmental cleanup contract. Some of the activities can be crashed. The tasks, durations (in days), costs, predecessor relationships, the crash times, and costs associated with performing the activities at their original (normal) times and for the crash times are shown as follows: Activity A B C D E F G H Immediate Predecessor ww A, B B C, D E E G Normal Time (days) 5 5 2 3 5 2 3 5 Normal Cost ($) 1,000 800 600 1,500 900 1,300 900 500 Crash Time 4 3 1 2 3 1 3 3 a. What is the critical path of the project? Show all work to earn full credit. b. Find the normal total project completion time. Show calculations. Crash Cost ($) 1,200 2,000 900 2,000 1,200 1,400 900 900 c. The project needs to be completed three days early. Which activities need to be crashed? Explain why do you select those activities. d. What is the project cost after crashing? Show calculations.