$\textbf{Soft question:}$ If the probability of a customer leaving the queue (system) is $\frac{1}{4}$, am I right to say that the departure rate of a single customer is $\mu=\frac{1}{4}$, and that the departure rate of $k$ customers is $k\mu = \frac{k}{4}$ in the $M/M/\infty$ system?
Some clarification will be great!