Show the id and builder of the railway that are associated with the most trains.
return railways ;return trains associated with  #1 ;return number of #2 for each #1 ;return #1 where #3 is  highest ;return id of #4 ;return builder of #4 ;return #5 , #6
['select', 'project', 'group', 'superlative', 'project', 'project', 'union']