Choose whether this statement is true or false and explain.

a. In a two-good world if one good is an inferior good the other good must be a luxury.

b. When the price of a good changes, the substitution effect can be found by comparing the equilibrium quantities purchased on the new budget line and a hypothetical budget line that is a shift back to the original indifference curve parallel to the new budget line.

c.A Giffen good must be an inferior good and all inferior goods are Giffen goods.