If you’re trying to decide on an answer to some HW problem, or something of the like, go with what’s more likely. If that is the case, is what you posted the *exact* wording of the question? If not, I recommend you provide the exact question, as it’d help greatly in deciding on an answer.
Simply from a human perspective, and based on questions I’ve encountered over the years, it’s much more likely that **c** is the dependent variable. But again, I’d need to see the exact wording to provide an exact answer.
Lastly, you mentioned a “packing food” scenario where yes, it does seem more intuitive for **c** to be independent rather than dependent.
So in short, what are you precisely asking? It can go either way depending on the *specific wording* of the question. If you want an answer, provide the exact wording of the question you want answered, because otherwise there are multiple answers.