Create a new file with the name "myfirstscript.sh". Write a new script that performs the following tasks in sequence;

1. Display the usernames of currently logged in users; sorted from a-z
   1. HINT: You will need to filter the output of the who command
2. Display a list of usernames who are logged into the system more than once
   1. HINT: usernames that are logged in more than once = not 'unique'
3. Display a list of usernames that have been logged in since yesterday

Also, provide the commands to;

1. Set read and execute permission for the user and member of the users group; read-only permission for others; and write permission for the user only
2. Run your script from its stored directory

Note: The output of your script must be self-explanatory. For example, the output for the users who are currently logged into the system must be preceded by a header like this: List of users who are currently logged in to the system in alphabetical order