questions I need help with for my Linux tools class.

1.) How would you display a list of users currently logged into the system, such that every username (and just the username) appears only once? Give exact syntax.

2.) How would you display all files in current directory that are newer than "file.txt"? Give exact syntax

3.) What is the 'time' command used for in Linux?

4.) How would you compress a file (using any of the Linux compression tools available) named "mydata.txt"? Give exact syntax.

5.) Using grep and regular expressions, how would you display the lines of a file named "mydata.txt" that end in A? Give exact syntax.