Consider a bank that has five tellers. The arrival rate of customers, $r_a,$ is $6$ people per minute. The effective processing rate

of each teller, $r_e,$ is $80$ people per hour. The utilization, $u,$ is:

$1\mathrm{.}2$

$0\mathrm{.}075$

$0\mathrm{.}015$

$0\mathrm{.}90$