Esperanza Rios worked as the Supervisor of the Billing Department for Fresenius Medical Care for two years, where she managed employee work flow and performance. A reference letter describes Esperanza as a bright, personable, highly motivated individual with a strong work ethic who performs well in fast-paced environments. The letter also notes that Esperanza has in-depth knowledge of medical billing processes and was able to quickly learn and apply new technologies in her work.