You have informed your users that you need to bring the machine down at the end of the day to perform routine maintenance. however, prior to shutting the system down, you want to give users fifteen minutes to save data and exit the system. in this lab, your task is to shut the machine down and warn your users as follows:
a. use a 15-minute delay before shutting down.
b. use it is time for a shutdown! as a message to all logged-in users.