Concept:
λ = Arrival rate (customer/time)
μ = Service rate (customer/time).
Average arrival time and the time spent in the system (Waiting time in system) = \({W_s} = \frac{1}{{\mu - \lambda }}\)
Average arrival time and the time spent in the queue (before being served) (Waiting time in queue) = \({W_q} = \frac{\lambda }{\mu }.\frac{1}{{\mu - \lambda }}\)
Calculation:
λ =12 customer/hr
μ = 24 customer/hr
\({W_q} = \frac{\lambda }{{\mu \left( {\mu - \lambda } \right)}} = \frac{{12}}{{24\left( {24 - 12} \right)}}\)
\(= \frac{1}{{24}}hrs = \frac{1}{{24}} \times 60 = 2.5\;minutes\)
