A question on a conventional t-distribution. See the details below please

(a) From time series data for the variable yr a researcher obtained the following regression results (standard errors in parenthesis): Ayr 231.030.188yr_1+u"r s.e. (12.50) (0.080) On the basis of these results and knowing that the 5% critical value for the Dickey-Fuller (DF) test is -2.95 and the 10% critical value is -2.60, is this variable stationary or non-stationary? Explain clearly how you construct the test and what is the null and alternative hypothesis. The corresponding critical values from the conventional t distribution are -1.645 (5%) and -1.128 (10%). Would you reach the same conclusion if you based your test on the conventional t-distribution? (6 marks} (b) Explain how the researcher should proceed, given the results obtained in (a). (4 marks)