"you know what?" or how to change your mind


What are some ways in which one can express "you know what?" expressions with
a nuance of either "i've made up my mind" after debating something internally
for awhile? I see that やっぱり or 実は are somewhat close but doesn't quite fit.

For example

A: "You going to the meet up tomorrow?"

B: "I'm not sure..."

A: "Well let me know before Friday"

B: "You know what? I'll go."




So you mean "you know what" used in this scene?
<https://youtu.be/rk_qLtk0m2c?t=2m58s>

It's difficult to give a direct equivalent, but possible expressions would be:

  * こうしましょう！ こうしよう！  
(This こう refers to something that follows.)

  * それじゃあ！ それでは！
  * では！ じゃあ！
  * 決めた！ 決めました！ わかった！ わかりました！
  * よし！ オーケー！




So you mean "you know what" used in this scene?
<https://youtu.be/rk_qLtk0m2c?t=2m58s>

It's difficult to give a direct equivalent, but possible expressions would be:

  * こうしましょう！ こうしよう！  
(This こう refers to something that follows.)

  * それじゃあ！ それでは！
  * では！ じゃあ！
  * 決めた！ 決めました！ わかった！ わかりました！
  * よし！ オーケー！

