A process includes four steps $($as shown below$).$ A separate person works at each of the steps and they use a $7$ hour work day shift."Step $1"$ takes $3$ min per order

"Step $2"$ takes $7$ min per order

"Step $3"$ takes $5$ min per order

"Step $4"$ takes $2$ min per order

What is the current maximum output of the whole process per day?

$60$

$84$

$140$

$210$

None of the above