Consider the following portion of monthly data on price per gallon of unleaded regular gasoline in the U.S from January 2009 to December 2010.

Year........................ Month................ Price Per Gallon

2009............................ Jan ............................$1.79

2009............................ Feb ............................1.92

⋮..................................... ⋮................................. ⋮

2010........................... Dec.............................2.99

a. Plot the above series to identify an appropriate polynomial trend model. You may ignore seasonality.

b. Compare the adjusted R2 of the linear, the quadratic, and the cubic trend models.

c. Use the appropriate model to make a forecast for the price of regular unleaded gasoline for January and February of 2011.