A server operates with $80\%$ utilization. The coefficient of variation for the service process is $0\mathrm{.}5$ and the coefficie variation of the arrival process is $1.$ The average processing time is $3$ minutes. What is the average time a custor waits in the queue according to the single$-$server queue model?

$3$ minutes

$3\mathrm{.}75$ minutes

$10\mathrm{.}5$ minutes

$7\mathrm{.}5$ minutes