During regular operating hours, passengers of Fly-Hi airlines arrival at the airport at the average rate of 190 per hour (Poisson distributed). Fly-Hi can hire staff for $18 per person per hour, each of whom can check in a passenger in an average time of 1 minute (negative exponential distribution). Fly-Hi has determined that the cost of waiting is $45 per passenger per hour. [Select] What is the minimum number of staff for this system? Select] What is the optimal number of staff for this system? What is the total cost of this system per hour at the optimal number of staff? [Select