In a waiting line system, arrivals occur, on average, every $20$ minutes, and $20$ units can be processed every hour. If $\backslash$lambda $=$ Mean arrival rate per hour and $=$ Mean service rate per hour, what are $\backslash$lambda and $?$

$\backslash$lambda $=3$ and $=20$

$\backslash$lambda $=20$ and $=20$

$\backslash$lambda $=20$ and $=3$

$\backslash$lambda $=3$ and $=3$