Answer:
d) the dining room where customers eat their meals
Step-by-step explanation:
In the given situation, since it is mentioned there is a Sammy's fast food restaurant that generates the sandwiches, soups, and other items for customers
So based on the options given, the last option should be considered as a fixed input for the production function as the dining room is a fixed plus non-movable item so the same is to be considered
hence, the correct option is d.