using Linux/Unix please, thnx in advance.

8. Give the command for removing an empty directory called personal under your home directory. How would you remove it if the personal directory is not empty?

9. Create a file, called sample, in your home directory and set its permissions to read and write for yourself, read for users in your group, and none to everyone else. What command did you use to create the file? What command did you use to set privileges?

10. Suppose that umask is set to 022 on a system. What will be the default permissions for the new directories and text files that you create? Explain your answer.

11. Assume that you have two files, f1 and f2, that you want to concatenate and store in a file called f1nf2. Show the cat command needed to perform this task. Now show the cat command (concatenate) needed to put your name, taken from the keyboard, as the last line of f1nf2.