which of all of them would you refinance today? Then pick the bottom answer at which you'd refinance (since everything above that rate you would also refinance.
If I had two houses at 4.5% and 4.75%, and I thought refinancing was worth it at 4.5% then I definitely would think it was worth it to refi at 4.75% because i'd save even more. Poll option would be 4.5% since everything above that would also be worth it