I just got my third MBA (first one bad screen, second frame around screen detaching and bending) and, unfortunately, the adapter is not working. I tried my girlfriend's macbook adapter and that worked so it's not the computer. What do I need to get the adapter replaced? Can I bring just the adapter into the store, or do I need the computer with me too? Also, is it safe to use the macbook adapter in the macbook air? Thanks!