During the summer months, a forest ranger working in an observation tower spots a possible fire on the average of once every day. Each such sighting requires the ranger to leave the observation tower and go to the scene of the potential blaze in order to take a closer look. According to Forest Service records, this process normally takes 4.8 hours. Forest rangers serve 24-hour shifts in the observation towers. If the Service is willing to risk no more than a one percent chance of a fire going undetected, how many forest rangers should staff an observation tower during a shift.