According to the [explanation](https://support.binance.com/hc/en-us/articles/115000583311), the rate for converting the trade receivable to BNB is updated every second.
1. How do we concretely get this rate through the API?
2. How is the "market price" written in same section determined? Is it going to be a market order to yield BNB? Or will the rate be something like the mean of the current bid and ask? Or the last done price?