Hi! I read a conversation in which someone told someone else that he could take another train (instead of the one that was about to leave). He said, "Dann können Sie eine Stunde später abfahren, um 14 Uhr 27; aber da müssen Sie in Stuttgart umsteigen." What does "da" mean? I can understand the rest of it: "Then you can leave an hour later, at 2:27 pm. But you (will) have to change (trains) in Stuttgart." Thank you in advance.