What's the appropriate definition for や in this lyric? Can anyone give similar examples of や? jisho.org has this definition (#4) "interjection expressing surprise" but that doesn't seem right.
僕達このまんまでいいんですか
おいどうすんだよ
もうどうだっていいや
This is from the song ロストワンの号哭 (the lost one's weeping)