笨小孩口语广播：一言为定!

 　　Heidi invited us to have a dinner, why?

　　第一个句子: I'll treat!==My treat! 我请客!

　　I want to invite you to dinner. I'll treat!

　　第二个句子: It's a deal! 一言为定!

　　第三个句子: Let's go fifty-fifty. AA制!

　　Reference:

　　a. Are you free tomorrow? I want to treat you to dinner.

　　b. Is it a deal?

　　a. It's a deal.

　　b. So see you at the old school gate.

　　a. See you and be there or be square!

　　b. See you!