Demand and the price of motor fuel from 2007 to 2008, the price of gasoline in the United States rose from $2.76 per gallon to $3.20 per gallon. The quantity used decreased from 3,389 million barrels to3,290 million barrels. In 2009, the price fell to $2.30 per gallon, yet the quantity used continued to decline, to 3,283 million barrels. After-tax personal income increased from 2007 to 2008, but it fell from 2008 to 2009. Which one or more of the following hypotheses do you think best explain(s) the pattern of gasoline sales? Illustrate your chosen hypothesis with an appropriate diagram.

a. In 2008, the demand curve for gasoline had the usual negative slope. However, in 2009, the demand curve shifted to a positively sloped position.

b. The demand curve had a negative slope at all times, but because gasoline is a normal good, the demand curve shifted to the right in 2008 and then to the left in 2009"