Many of a bank$$s customers use its automatic teller machine to transact business after normal banking hours. During the early evening hours in the summer months, customers arrive at a certain location at the rate of one every other minute. This can be modeled using a Poisson distribution. Each customer spends an average of $89$ seconds completing his or her transactions. Transaction time is exponentially distributed. c$.$ Determine the average number of customers waiting to use the machine. $($Round your answer to $2$ decimal places.$)$