In the aftermath of the September 11, 2001, terrorist attacks on the World Trade Center, the New York City Department of Design and Construction was put in charge of recovery and clean-up operations at the site. The attack killed 2,823 people, destroyed a total of 8 buildings, and crushed 1,300 feet of subway tunnel. Ultimately, the clean-up operations involved four construction firms, 3,000 workers, and 3.1 million man hours. It took more than 100,000 truckloads to carry the 1.8 million tons of debris from the site. Amazingly, no workers were killed or critically injured during the clean-up effort, which officially ended on May 30, 2002, at a cost of $650 million. (Source: www.pbs.org/americarebuilds) Obviously, a project of this magnitude could not be completed successfully without careful planning and coordination of many, many activities. Indeed, many clean-up "activities" could be considered subprojects of the entire clean-up operation. Imagine that you were the person in charge of the clean-up operations at the World Trade Center site. No one has ever faced this task before, so no one can give you a nice, neat list of things to do with precise time estimates for each activity. It is an enormous task requiring careful consideration of human emotion, dignity, and safety concerns in addition to the monumental logistics and financial issues. And the world is watching all you do. Identify the key top-level activities you think would go into the clean-up project and prepare an AON project network summarizing the precedence relations among these activities. Also, describe how you would go about estimating the activity times and financial costs associated with these activities.