) Make an Excel graph of the data on U.S. online advertising spending. (b) Discuss the underlying causes that might explain the trend or pattern. (c) Use Excel, MegaStat, or MINITAB to fit three trends (linear, quadratic, exponential) to the time-series. (d) Which trend model do you think is best to make forecasts for the next 3 years? Why? (e) Use each of the three fitted trend equations to make a numerical forecast for 2007. How similar are the three models' forecasts?