Q:  What is the maximum redshift in this set of objects?

              z  =  9       (roughly)


  Q:  What is the light-travel time for a galaxy at that redshift?

              13.169 Gyr



  Q:  If the universe is 13.8 billion years old, what is the maximum
            possible age for a galaxy at that redshift?


               age  =  13.8 Gyr  -  13.169 Gyr  =  0.63 Gyr

                                                =  630 million years