Tell me the ages of the oldest and youngest students studying major 600.
return students ;return major of  #1 ;return #1 where #2 is  600 ;return ages of  #3 ;return #1 where #4 is  highest ;return #1 where #4 is  lowest ;return #5 ,  #6 ;return ages of  #7
['select', 'project', 'comparative', 'project', 'superlative', 'superlative', 'union', 'project']