Kamel, please note this extract from the forum guidelines;
Originally Posted by kamel2
You are welcome to reply to any of the questions posted in the Ask a Teacher Forum, even if you are not a teacher. In fact, your answers and contributions are most welcome. However, you will need to state clearly in your post that you are not teacher. Please remember, the person whose questions you are answering or whose thread you are contributing ideas to believes the help is coming from a teacher.
Please do not edit your question after it has received a response. Such editing can make the response hard for others to understand.