Kevin works as a clerk at a firm that provides investment services to customers, and earns around $40,000 annually. Upon joining the firm, Kevin had to go through only a brief period of on-the-job training as the job requires him to perform mechanized tasks that require little skill beyond basic literacy. In the context of the Weberian model of the U.S. class structure, Kevin most likely belongs to the __________. upper class working class middle class upper-middle class