Customers arrive at Rich Dunn's Styling Shop at a rate of $2$ per hour, distributed in a Poisson fashion. Service times follow a negative exponential distribution, and Rich can perform an average of $6$ haircuts per hour. a$)$ The average number of customers waiting for haircuts $=0\mathrm{.}17$ customers $($round your response to two decimal places$).$ b$)$ The average number of customers in the shop $=$ customers $($round your response to two decimal places$).$