find travel arrangements for a round trip flight from baltimore to pittsburgh after 8 o'clock pm before 10 o'clock pm 
return flights ;return #1 from  baltimore ;return #2 to pittsburgh ;return #3 after 8 o'clock pm ;return #3 before 10 o'clock pm ;return #3 in both #4 and  #5 ;return #6 that  is  round trip ;return travel arrangements of #7
['select', 'filter', 'filter', 'filter', 'filter', 'intersection', 'filter', 'project']