General Autos sold a record number of automobiles last year. Will General Autos bring in another record this year? Well, an automobile is sold either within the United States or sold overseas in international markets. Abroad, automobiles have been sold this year at well below last year's record pace. At the same time, there is considerable evidence that the number of overseas offices opened will be no higher this year than it was last year, and surely the new overseas offices opened this year will sell no more automobiles per office location than did last year's overseas offices. Clearly, it can be concluded that the incremental number of automobiles sold this year will fall short of last year's record.
In the argument given, the two portions in boldface play which of the following roles?