If the value of trading goods reaches the Nisab in both established currencies, from which currency should Zakat be paid?

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If the value of the trading goods reaches the Nisab according to both circulating currencies, the owner may choose the currency from which to pay the Zakat (one-quarter of a tenth of its value). However, it is preferable to pay from the currency most commonly used in the locality, as this is more beneficial to the poor. If both currencies are equally in use, the owner may choose either.