In Example $5.3$ if server $i$ serves at an exponential rate $\lambda_{i}, i=1,2$, show that
$$
P\{\text { Smith is not last }\}=\left(\frac{\lambda_{1}}{\lambda_{1}+\lambda_{2}}\right)^{2}+\left(\frac{\lambda_{2}}{\lambda_{1}+\lambda_{2}}\right)^{2}
$$