A waiting $-$ line system that meets the assumptions of M $/$ M $/$ S has $\backslash$ lambda $=5,\backslash$ mu $=4,$ ?and M $=2.$ ?For these values, Po is approximately $0\mathrm{.}23077,$ ?and Ls is approximately $2\mathrm{.}05128.$ ?What is the average time a unit spends in this system?

Select one:

a $.$ ?Cannot be calculated because $\backslash$ lambda is larger than $\backslash$ mu $.$

b $.$ ?approximately $0\mathrm{.}2083$

c $.$ ?approximately $0\mathrm{.}1603$

d $.$ ?approximately $0\mathrm{.}4103$

e $.$ ?approximately $0\mathrm{.}8013$