Final answer:
Ruth's job at Graham Mailing Services falls under the field of Business, specifically in a management position within the organization.
Step-by-step explanation:
The role described for Ruth, which involves supervising employees and ensuring that they perform their job well, falls under the field of Business. Specifically, Ruth's job can be classified as a management position within a business organization. As the second-in-command at Graham Mailing Services, Ruth is responsible for overseeing employee performance and ensuring that the mailing tasks are completed according to customers' specifications.