What is the Zakat liability when two parties each own the Nisab but mix only a portion of it?

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If two men each own sixty sheep and mix only twenty sheep with each other, one sheep is due between them, split equally. If the mixed amount is less than this threshold, the ruling of mixture does not apply, and each owes a full sheep individually. However, if they mix forty sheep, with one contributing ten and the other thirty, the ruling of mixture is established because the presence of the Nisab is fulfilled in the mix.