Exercises

1. My friend just created a file in his/her directory. Can I go and change permissions on it Why, or why not
2. I just created a new file in my directory, but I would like it to have rwx permissions for me, and r permissions for everyone else. What command can I use to change those permissions
3. I have a file with permissions rwxrwxr-x. I want it to have rwxr-xr-x permissions. What commands (I want two) can be used to change the permissions on it
4. Take the same file. I want to remove all execute permissions for everyone, except myself. Again, which command can be used to achieve my goal