Those who were not able to continue following the imaam in Friday prayers because the electricity was cut off
Question

                A group of people were praying Jumu’ah in the basement of the mosque, and during the prayer the electricity was cut off and they could no longer hear the imaam. One of the worshippers stepped forward and led them in the rest of the prayer. What is the ruling on their prayer, knowing that he completed the prayer as Jumu’ah (i.e., two rak’ahs)? 

What would be the ruling if no one had stepped forward to lead them? Should each person have completed the prayer on his own? If that is permissible then should it be completed as Zuhr (four rak’ahs) or Jumu’ah (two rak’ahs), since they had listened to the khateeb and had started the prayer with the imaam and prayed one rak’ah with him?
Praise be to Allah. 
          If the situation was as described by 
          the questioner, then the prayer of all of them is valid, because whoever 
          catches up with one rak’ah of Jumu’ah has prayed Jumu’ah, as it says 
          in the saheeh hadeeth narrated from the Messenger of Allaah 
          
          (peace and blessings of Allaah be upon him). If one of them had not 
          stepped forward and they had each prayed the final rak’ah alone, that 
          would have been OK, as in the case of one who joins the prayer in the 
          second rak’ah with the imaam, then makes up the other rak’ah by himself 
          – because of the general meaning of the hadeeth in which the Prophet 
          
          (peace and blessings of Allaah be upon him) said: “Whoever catches up 
          with one rak’ah has caught up with the prayer”. And Allaah is the Source 
          of strength.