3. Customers arrive at a full-service one-pump gas station at rate of 20 cars per hour. However, customers will go to another station if there are at least two cars in the station, i. e., one being served and one waiting. Suppose that the service time for customers is exponential with mean 6 minutes. (a) Formulate a Markov chain model for the number of cars at the gas station and find its stationary distribution. (b) In the long run, how many customers are served per hour