Теория:

Study some information about the difference between the Future Perfect and the Future Perfect Continuous.
 
 
Future Perfect Continuous 
                                                                       
   Future Perfect
 
Действие длится в течение определённого времени на момент будущего
  
Действие завершится к какому-то указанному моменту в будущем
 
By May Jenny will have been writing her essay more than six months
  
  
By May Jenny will have already written her essay
                                                                   
 
                will have been Ving
 
                will have V\(3\)/Ved