$3-$ A simulation model of a G$/$G$/1$ queuing model was run for $10$ min. The area under Q$($t$)$ graph is $10$ units and Q$(10)$ equals $0.$ The number of entities served or being served is $5.$ What is the average waiting time of the entities in minutes $?$

a$\mathrm{.}1$

b$\mathrm{.}2$

c$\mathrm{.}3$

d$\mathrm{.}4$ e$\mathrm{.}0\mathrm{.}5$