Final answer:
The total cost of Judy's purchase is calculated as C = np + f, where C represents the total cost, n is the number of boxes, p is the price per box, and f is the fixed fee. None of the given choices match this equation.
Step-by-step explanation:
Judy's total cost (c) for n boxes of cereal at p dollars per box, plus a fixed fee (f), is represented by the equation C = np + f. This equation shows that the total cost is proportional to the number of boxes she buys, with p representing the proportionality constant, and f being the additional fee that does not depend on the number of boxes purchased. Since there are no options provided that match the form of this equation, none of the answers A) C=80, B) C=120, C) C=130, or D) C=150 are correct. However, if we were to assume that np represents the total before the fee, and f is the fixed fee, then we can infer that the correct equation to represent the Judy purchase scenario would simply be C = np + f, which is not listed among the provided choices.