What are the usernames and passwords of users that have the most common role?
return roles ;return users of #1 ;return number of  #2 for each #1 ;return #1 where #3 is  highest ;return users of #4 ;return usernames of #5 ;return passwords of #5 ;return #6 ,  #7
['select', 'project', 'group', 'superlative', 'project', 'project', 'project', 'union']