Use the text below to answer the next four questions:

A taco truck manager wants to get more lunch time customers, but doesn't know how much

time it takes to process a single customer. The amount of time it takes to process a single

customer will help the manager determine the maximum number of customers they can

process in the lunch hour. On average, during lunch hour, $12$ customers are in line $($i$.$e$.$

process$)$ waiting to order at the window. Four customers per minute receive their food and

leave the line $($i$.$e$.$ exit the process$).$

Question $1$

On average, what is the inventory, I $($number of flow units, customers$),$ of the line$/$process

during the lunch hour?

$12$

$36$