Do I need to get a replacement bike for this broken chainring? I wanted a cheap commuter bike, and just received this bike from Amazon. I have little knowledge about bikes, but looks like the middle chain-ring is broken to me. 


Is this indeed broken, or is it something that is not too big and can be safely ignored? (I am still to get my tools so haven't yet assembled the bike, so can't say if it shifts/rides alright in that ring.)
If it is not something to worry about for now, how long do will it last till major problems start showing? 




(Larger version of the picture here.)
Those notches are used when shifting gears, as you move the derailleur, the chain moves and catches on a notch and switches from one chainring to another adjusting the gearing.

You do not need a replacement bicycle, this is a nice bike and with proper maintenance (keeping the drive train clean and lubed) should last a long time.