2. The ABC department store has a dock which is designed to service only one truck at the same time with two workers and the queuing trucks are increasing recently. The average arriving rate of truck per hour is four and the service rate per hour is six.

(1) Calculate the characteristics (such as average service rate, worker utilization rate, the probability of workers break time, average number of truck in system, average of trucks consuming time in system, average number of trucks in queuing, average of trucks consuming time in queuing and the probability that arriving truck should be waiting) of this queuing model according to workers from 2 to 6.

(2) Determine the optimal number of workers from 2 to 6 in this queuing system using the following cost

information .

- truck cost per hour: $2,000

- workers wage per hour: $1,000