Is it permissible to perform the Prayer of Fear by having each contingent complete a separate, complete prayer?

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It is permissible for the Imam to pray two Rak'ahs with the first contingent, conclude the prayer with Taslim (salutation), and then the first contingent departs to guard while the second contingent prays two Rak'ahs behind the Imam and concludes. This method, attributed to Abu Bakra, is considered a good method, simple, and does not require separation from the Imam or defining the specific form of the prayer. In this case, the Prophet performed four Rak'ahs in total, and the companions prayed two Rak'ahs each. This means the Imam is offering voluntary prayers while leading those performing the obligatory prayer in the second Rak'ah.