Bob Johnson was hired to drive an airport shuttle bus for a rental car company back and forth from the airport to the rental car company’s off-site parking lot. When Johnson was hired he signed a written contract that specifically stated that he was an independent contractor, He was paid every two weeks, based on a rate per mile plus an hourly rate for waiting time. Johnson drove the shuttle bus at times and locations as directed by the rental car company, and he was on-call 24 hours per day except for Mondays and Fridays. Is Johnson an employee or an independent contractor? Explain the basis for your conclusion.