Final answer:
The correct answer is the amount made from selling the candy bars; {0, 1, 2, 3, ..., 800}.
Step-by-step explanation:
To find the amount made from selling candy bars, we can substitute the given function P = 3C - 400, where C represents the number of candy bars. We are given the set of all possible values for C, which is {0, 1, 2, 3, ..., 800} in option a. Therefore, the correct answer is a) the amount made from selling the candy bars; {0, 1, 2, 3, ..., 800}.