A new patient can come and directly sees the doctor without having to queue.

$(6$ marks$)$

$($b$)$ The doctor is busy.

$(3$ marks$)$

$($c$)$ There is no queue.

$(4$ marks$)$

$($d$)$ There are ten people in the system.

$(3$ marks$)$

$($e$)$ There are more than two patients in the system.

$(5$ marks$)$

$($f$)$ There is maximum of two patients in the queue.

$(4$ marks$)$