Question

Look at the table the utility of macaroni and cheese. carmen loves macaroni and cheese for thanksgiving. carmen's marginal utility from eating macaroni becomes negative at the _____ serving.

Answer 1

the marginal utility become negative at  Sixth serving.
After consuming a same product for a number of times, our satisfaction of consuming the product will start to decrease (in this case, it because Carmen started to feel full and maybe nauseated due to the amount of Mac and cheese that she'd been consuming)