No idea. Assuming not if it's an extra you buy. I bought my iPhone from Apple though, not on contract.
If you didn't buy AppleCare + at the time! this is going to cost you 269 $
You could find a third party shop that fix it for you for less money, but it will void your warranty.
How would they know the screen is replaced?
I can't afford that!
Although my iPhone is still under warranty I don't think apple cover this,
how much do they charge?
b) is there a a cheaper option as I'm not in a good financial position right now
Very dangerous if he lacks experience .... If you have to void the warranty, let some professionals do it for you