Consider a DASH system for which there are N video version (at N different rates and qualities) and N audio versions (at N different rates and versions). Suppose we want to allow the player to choose at any time any of the N video versions and any of the N audio versions. If we create files so that the audio is mixed in with the video, so the server sends only one media stream at any given time, how many files will the server need to store (each a different URL)? If the server instead sends the audio and video streams separately and has the client synchronize the streams, how many files will the server need to store?