please show me the cost of flight ua 201 from boston to denver and flight ua 343 from boston to denver 
return flights ;return #1 on  ua  201 ;return #2 from  boston ;return #3 to denver  ;return #1 on  ua  343 ;return #5 from  boston ;return #6 to denver  ;return #4 , #7 ;return costs of #8
['select', 'filter', 'filter', 'filter', 'filter', 'filter', 'filter', 'union', 'project']