The ruling on one who sold gold and did not pay its zakah

I sold some old gold and had not paid its zakah before. Please clarify for us how its zakah is calculated? And if I sold it for four thousand riyals, do I pay the zakah from this amount?
Answer: If you did not know that zakah is obligatory until after that, then you owe nothing. But if you knew that, then pay zakah on these four thousand: twenty-five from every thousand for the single year, twenty-five from every thousand, which is a quarter of a tenth, and likewise for the years before that according to the value of the gold in the market. The obligatory amount is a quarter of a tenth, and you pay this zakah in the known currency.
As for if you did not know that until the last year, then you owe zakah for the last year: twenty-five from every thousand. Yes.