Formula: If cell 3 is blank have cell 1 calculate, if cell 3 filled have cell 2 calculate

Bare with me, I am not sure the best way to word this.

Currently column I(uncompleted) calculates days between current date and whichever date is later between columns E(Scheduled) and F(Arrived).
I would like column I(uncompleted) to continue doing this unless there is a date in column K(Notification).
Once there is a Date in column K(Notification) I would like column I(uncompleted) to become blank and then I would like column J(completed) to calculate days between column K(Notification) and the later date between Columns E(Scheduled) and F(Arrived).

Attached is an example that I hope will help you all to understand what I am wanting to do.

Let me know if you need more info to help clarify it more.

Thank you both, those work great!

I know this is marked solved already, but is there an easy option to add to the formulas where when if there isn't any data entered yet, column I and J will be blank or display a zero?
I can make a new post if needed, just thought might be easier here since you two understand the current formula and what am I trying to do.

Attached is an example showing data in the formula fields while the input data fields are blank.
I tried you suggested new formula but it was displaying the same thing.

Thank you so much... Your a life saver!