In preparation for answering the questions, enter the search term "artificial intelligence gate assignment O'Hare" into Google and review some of the articles returned by Google.
There are many variables, which change frequently. Security is involved. Some airplanes will fit at only some gates. Capacity (number of gates) is limited because each gate is expensive, even at the biggest airports. It is costly to have a plane waiting to deplane passengers or to depart.
The system uses the rules established by the experts in the task of gate assignments. The system acts on actual information provided by radio transmission from the airplane in real time.
The case explicitly states three. See question #2. There are many more, e.g., the system can be used to train people; the incidental operator does not need to be an “expert” – just use the ES as designed; the real expert can override it and provide “new” solutions, etc.
Many other systems need to use limited capacity facilities. For example, bus stations, harbours, and any where there is queuing. The potential for ticket lines and supermarket checkouts is worth investigating.