Using the arrival rate data of $12$ requests per hour and service rate of $15$ requests per hour from Problem $2,$ now use two desks in the library and determine:

a$)$ Calculate all Operating Characteristics.

b$)$ If the cost for the service is $$15$ per hour and the cost of waiting time for each customer is $$10$ per hour before being served. Calculate the total cost with one desk and with two desks.

c$)$ Should the campus expand the system to two desks? Explain.