What is the waiting period required if the death of one husband is known but the time of death of the other is unknown, or if both deaths are unknown?

Primary text

She must observe two waiting periods from the moment the first death became certain, beginning with the waiting period for the husband whose death was first known or deemed primary. If she is pregnant, the waiting period for the second husband concludes upon the delivery of the child, as the child belongs to him. Following that, she commences the waiting period for death for the remaining husband, which is four months and ten days.