This is classical conditioning.
The conditioned stimulus is, at first, entering the cafeteria. Later it becomes hearing the lunch bell ring.
The conditioned response is bill feeling hungry.
Answer:
black and white and your's dude
Countries trade with each other when, on their own, they do not have the resources, or capacity to satisfy their own needs and wants. By developing and exploiting their domestic scarce resources, countries can produce a surplus, and trade this for the resources they need. You can integrate all of this into your question. Hope this helped.
I think that the answer is that he like around 34