How do you calculate this, if you have multiple purchases of Bitcoin at different prices, all in the same wallet and then sell part of your holding? For example, 10,000 sats bought at $10k, 5000 at $20k and 12000 bought at $28k and you sell 7500 sats at $24k? What is my gain or loss? Would my accountant even know the answer? Is there an equivalent calculation with, say, gold bullion?