In an M$/$M$/2$ queue model with $\backslash$lambda $=10$ customers$/$hour and $\backslash$mu $=8$ customers$/$server$/$hour$,$ what is the average time a customer spends in the system?

Question $11$ options:

$0\mathrm{.}1$ hour

$0\mathrm{.}125$ hour

$0\mathrm{.}25$ hour

$0\mathrm{.}5$ hour

None of the above