吧
ba
Conceding with "ba"
吧 also signals reluctant agreement — "fine then".
那 + Statement + 吧
How it works
那好吧 is the sound of giving in. 好吧 on its own does the same job.
The tone is the whole point: the speaker isn't enthusiastic but is going along with it.
Examples
nà hǎo ba
那好吧。
Fine then.
hǎo ba, wǒ qù
好吧，我去。
Alright, I'll go.
nà jiù zhè yàng ba
那就这样吧。
Let's leave it at that then.