This question is currently tagged with homework. I had previously removed this tag from some other questions, but since it keeps reappearing, it is probably best do discuss it here on Meta.
The topic has been mentioned before by ymb1 in this Meta post:
On a related note, the tag homework was created, but I deleted it, as it is an orphan tag, and I don't see what value it adds to the question, whether it's on or off-topic (feel free to discuss this point as well).
But there was no discussion on that particular point. I tend to agree with this, it is a meta tag that adds nothing relevant to the question. What do you think?