VIDEO: Only about 40 percent of buildings in Knox County that are covered by Rural/Metro Fire are included in the voluntary subscriptions that fund the company's fire and emergency services operations. Those subscriptions average about $400 each year, according to R/M spokesperson Jeff Bagwell, who said the company relies on the square footage of living space on a property to determine rates for residences. “It depends on what those structures are to determine what we’re going to assess value to and have a subscription for,” Bagwell said. “An average subscription in Knox County is about $400 a year. That’s on average; obviously a single-wide trailer is going to be much less.”