The worksheet "Datal" of the Excel file "CentralEnglandTemp2016" shows the monthly mean (surface air) temperatures for the Midlands region of England between 1750 and 2016. (The shown temperatures are in Celsius degrees measured with a precision of 0.1 C.) The data set represents the longest reliable series of monthly temperature observations in existence, and hence is the most valuable source of information for meteorologists and climate scientists. It was originally published by Professor Gordon Manley in 1953, and has been subsequently updated until today. 1. Define 12 dummy variables corresponding to 12 months (Jan, Feb,..., Dec). Since the categorical variable Month has 12 levels (categories), delete the dummy variable Dec, to assume the regression model with linear trend and seasonality: Temp=Bo+B Jan+ Feb+...+ Nov+t+ E 11 12 in which t = time period and is the random error term; see the worksheet Data2. Explain why the dummy variable Dec could be deleted.