How much does it cost for apple to replace a shattered back on iPhone 4S?

Unfortunately I managed to drop my 18 month old iPhone 4S this morning and the back has shattered. I've never had a case on this phone, and this is the first time I've shattered it. How much would it cost for apple to replace a shattered back?

You can pay Apple $50 to do it, or you can do it yourself for $20. Order a new OEM back cover from this site.http://www.m.gadgetmenders.com/Black_Glass_Back_Cover_For_iPhone_4S.html

The back is a simple repair.
1. Remove the two screws at the bottom of the phone, on opposite sides of the sync port.

2. Push the older back cover in an upward direction, and remove it.

3. Install new back cover

4.Re-insert the two screws on opposite sides of the sync port.

It's really easy and saves money. You can order a new back off of a different site, like Amazon or eBay for example, but they won't be OEM quality parts, which means they'll either shatter easier, or something minor will be wrong with it, like the apple logo being backwards, slightly crooked, or no apple logo at all. It's best if you order from gadget menders. Hope this helps.