What is the name and capacity for the stadium with the highest average attendance?
return stadiums ;return attendances of #1 ;return average of #2 for each  #1 ;return #1 where #3 is highest ;return name of #4 ;return capacity of #4 ;return #5 ,  #6
['select', 'project', 'group', 'superlative', 'project', 'project', 'union']