b.) what is the average time to be serviced. (problem must be worked on excel)

One mechanic services 6 drilling machines for a steel plate manufacturer. Machines break down on an average of once every 3 working days, and breakdowns tend to follow a Poisson distribution. The mechanic can handle an average of one repair job per day. Repairs follow a negative exponential distribution a) On the average, how many machines are waiting for service? The average number of machines waiting for service is (Round your response to three decimal places)