4.4 Use supply-and-demand diagrams to illustrate the qualitative effect of the following possible shocks on the U.S. avocado market.

a. A new study shows significant health benefits from eating avocados.

b. Trade barriers that restricted avocado imports from Mexico are eliminated (“Free Trade Party Dip,” Los Angeles Times, February 6, 2007).

c. A recession causes a decline in per capita income.

d. Genetically modified avocado plants that allow for much greater output or yield without increasing cost are introduced into the market.