I am a newbie here in stack exchange. This site is very informative. So, I tried to contribute with the little knowledge I have.
So, I posted this answer after reading the question, all the other answers and the comments of the OP.
I really don't know where I've done wrong. But, I am downvoted. I confirmed from the teacher after that : he said it was good enough.
I think this is the dark side of PSE that they don't value the new users here.
Does this happen with most of the new comers ?
In case if I've made anything wrong in my answer, please point out. I'll be pleased.