(a) What is the difference between a normal good and an inferior good?

(b) What is the difference between an iso-cost curve and an isoquant curve in the producer's optimization graphs

(c) What three assumptions allow economists to represent consumer preferences with a utility function?

(d) Consider the utility function u(x, y) = x + 2y. Write down any other utility function that represents the same preferences. Explain why the preferences are the same!