Vehicles leave an airport parking facility (arrive at parking fee collection booths) at a rate of 600 veh/h (the time between arrivals is exponentially distributed). The parking facility has a policy that the average time a patron spends in a queue while waiting to pay for parking is not to exceed 15 seconds. If the time required to pay for parking is exponentially distributed with a mean of 10 seconds, what is the fewest number of payment processing booths that must be open to keep the average time below the acceptable limit? (a) Find answer using M/M/n formula (b) Find answer using Tables (c) Find the processing rate that solves the problem utilizing only 1 server