Clarification on BNB Deduction Calculation Process

I am reaching out regarding the section on how to calculate fees when “Using BNB Deduction” is enabled, as outlined in the Binance support page at https://www.binance.com/en/support/faq/how-to-use-bnb-to-pay-for-fees-and-earn-25-discount-115000583311.

In the explanation provided, it is mentioned that when converting the original fee to BNB, assets are first exchanged to BTC, even if there exists a pair with BNB. ETH is used as an example, and the formula for the calculation is outlined as follows:

Exchange ratio of ETH/BNB = ETH/BTC[market price] / (BNB/BTC[market price])

I have a few questions regarding this process:

  1. Must all conversions be taken to BTC first, even if a pair with BNB exists for the respective asset?
  2. What happens if an asset does not have a BTC pair? How is the conversion handled in such cases?
  3. How is the market price, as indicated in the calculation, obtained? Are there specific API endpoints used for this purpose?