Well.....
...you do seem to admit that you broke it, so to be 100% honest this really wouldn't be something Apple should be responsible for.
But...the plastic/polycarbonate housings on the MacBook's have been known to have cracking & breaking issues...so depending on how it got broken, such as:
- got ridden over by a car
- dropped from a 2nd or 3rd floor window
- dog chewed on it
- you stepped on it
- etc.
...you may have a valid reason to check with Apple to see if they will fix it under warranty.
Hope this helps,
- Nick
Actually, my brother broke it