How is zakat assessed on money sent in a foreign currency if its exchange rate changed between the date of remittance and the date zakat became due, and is the exchange rate in the parallel market considered?

Zakat is obligatory on wealth if it reaches the nisab and a full year has passed on it. The nisab is estimated at the value of 85 grams of gold or 595 grams of silver. Zakat is to be given at a rate of a quarter of a tenth (2.5%) of the total amount, regardless of changes in the exchange rate. The most complete approach is to adopt what is most beneficial for the poor.