The what and why's are above my head at the moment, but that is how I learn sometime... one day I will understand more.
Out of curiosity I copied your question into chatgpt and I got this:
chatgpt:
To calculate the fair value implied volatility for KO (The Coca-Cola Company) given the provided information, you can use the concept of implied correlation and relative implied volatility. Here's the formula:
KO Ivol = PEP/USD Ivol * (PEP/KO Ivol) / (PEP/USD and KO/USD Implied Correlation)
Let's plug in the values given:
KO Ivol = 30% * (9%) / (80%)
KO Ivol = 0.3375 or 33.75%
Therefore, based on the provided information, the fair value implied volatility for KO would be approximately 33.75%.
Please note that this calculation assumes that the implied correlation and relative implied volatility remain constant and that other factors influencing option prices are negligible. It's important to consider this as a basic estimation, and market conditions may vary.
-----------------------
never know it helps, as you mentioned that you expected it to be simple.
I can go back to decipher the "what and why" now...