of the flights available from dallas to baltimore on august third which airline has the least expensive flight 
return flights ;return #1 from  dallas ;return #2 to baltimore ;return #3 on august third ;return price of #4 ;return #4 where #5 is the  lowest ;return airline of #6
['select', 'filter', 'filter', 'filter', 'project', 'comparative', 'project']