Data: airfare.csv (download from Module 4 on Brightspace) Every quarter, the Bureau of Transportation Statistics (BTS) takes a survey to track domestic airfares. This time series shows average airfares calculated from BTS (inflation adjusted to 2018 dollars) for U.S. domestic flights from 2004 to 2018. Background: For this part of the assignment, you work for a large airline (in 2018) and you would like to forecast 2019 average annual airfare in order to inform your airline's pricing strategy. Your business question is: "What is a reasonable forecast of 2019 average U.S. domestic airfare given the patterns in past data