I just bought a really nice, barely used cruiser (single speed) off craigslist for $180. It would be fine for a 3 km commute that was flat. With hills, you'll need gears. I agree with all who said to try to find a used bike as $200 is a very small amount to pay for a bike. If you don't know your size pretty much to a "t", I'd avoid ebay. With craiglist, at least you can take it on a short test ride. Also, many bike shops offer a small selection of used bikes.

Good luck!