Translation:Vâng, tạm biệt.
Since it doesn't appear this has been answered yet, what denotes that "Ừ" must be used here instead of "Vâng" when you use chào at the end? I've never even seen Ừ before, and it doesn't exactly explain why it CAN'T be used. Thanks! =)
Yes. In Northern dialects, people use "vâng" for "yes" while people in Southern dialects use "dạ" instead.