What is the aim of the announcement?

Could I have your attention everyone? An emergency situation has occurred on the tenth floor， and I ask everyone at this time to leave what you are doing and proceed toward the nearest exit out of the building. This situation does not pose any immediate danger，but as a safety precaution，we are asking everyone to evacuate the building. So，please do not panic，but walk calmly to the nearest staircase out of the building. Please do not take the elevators. Now，once you are outside，please make sure all the members of your department have arrived safely. If by any chance anyone is missing，please report the missing person to your immediate supervisors. Thank you，and we will let you know the progress of the situation as it occurs.
Number 71.What is the aim of the announcement?
Number 72.What are the people asked to do?
Number 73.When should a listener talk to the supervisor?