2. Build ARIMA models for the dataset 2a and 2b, using the steps outlined in class as a guide. If there are two [or more) competing models, make sure you discuss each of these. Make a decision about which model you think is best and support this decision with plots and other information. Here are short sumniines about the datasets to analyze. (a) The data in comdat are the daily morning temperature readings for a cow. (b) The data in bicoal .dat are the annual bituminous coal production levels in the US from 19304968 in millions of net tons per year