What are the names of every person who has a friend over 40 and under 30?
return people ;return friends of #1 ;return #1 where #2 is  over 40 ;return #1 where #2 is  under 30 ;return #1 of both #3 and #4 ;return names of #5
['select', 'project', 'comparative', 'comparative', 'intersection', 'project']