Consider a walk-in barber shop in downtown Raleigh. Currently there are three barbers serving customers and customers are happy to have their hair cut by the first barber available. On average, service takes 20 minutes per customer and a customer arrives every 10 minutes. We can assume that customers arrive according to a poison process and service times are exponentially distributed. Marketing studies reveal that customers visiting this shop value their time at $30 per hour. Calculate the total long-run average waiting cost per hour incurred at this shop.