Dexterity Business School Provides Short-Term Training Workshops to a Variety

Dexterity Business School provides short-term training workshops to a variety of corporations, out of a chain of small centers across the country. The instructors leading the workshops are hired on a contingent basis, and paid a set lump sum for each program. A supervisor at each location is responsible for recruiting instructors and providing them with Dexterity's prepared teaching materials. At the Canal City location, Andy Ashe has been leading these workshops for several years, and has been asked back several times by local businesses who find his workshops especially popular because of his verbal skills and keen sense of humor. The supervisor, Charlotte Monahan, has found that while her location contracts with several other instructors, businesses often ask for Ashe by name, even agreeing to postpone their contracted sessions until he is available. Dexterity's policies state that all contingent instructors are paid the same rate per workshop. Nevertheless, Ashe is aware of his popularity, and requests that Monahan start giving him a higher rate for his workshops.
Which of the following, if true, would most strengthen Dexterity's case in maintaining Ashe's current contract rate?
Monahan has never directly observed Ashe's performance in presenting a workshop.
As a contract worker, Ashe does not receive medical or retirement benefits.
Monahan has few applications from other qualified instructors in the area.
Dexterity uses a single-rate system for contingent workers.
There is no other agency in Canal City with whom Ashe could contract to provide similar workshops.