Is there a symbol for "risk free rate"

2 different strikes => call/put parity => 2 equations with 2 unknowns. Feel free to ask for the details. In practice, you would do the same for every strike with a tight bid/ask spread you could find to get an accurate number. Really nothing new here.

 

Indeed, you're correct... I must be getting senile.

 

It's a possibility you can't move away...