The purpose of tis forum is to test your posts not to actually get an answer.
If this is a real question then post it in SQL & PL/SQL forum.
Before, Please read OraFAQ Forum Guide and How to use [code] tags and make your code easier to read.

Note that we don't give solution to homework but we can help you to achieve it if you show what you already tried and where you are stuck.
Also have a look at SQL FAQ.