calc$\_$lq$\_$mmc$($lamda$,$ mu$,$ c$=1)-$ Calculates the average number of customers waiting for an M$/$M$/$c

queue. Your function should have a condition that, based on the number of servers, uses either the

simpler calculation for single server queues or the more general calculation $($that involves the

summation$)$ for multi$-$server queues. Defaults to a single service queue if c is not specified.

$L_q=\{\begin{array}{ccc}\frac{{}^2}{(-)}& \text{f}\text{o}\text{r}& c=1\\ \frac{r^c}{c!(1-{)}^2}{p}_0& \text{o}\text{t}\text{h}\text{e}\text{r}\text{w}\text{i}\text{s}\text{e}& \end{array}$

Return values:

$,L_q$ for valid, feasible queues

math.nan for invalid queue

math.inf for infeasible queue