\fProblem 2. [3 marks] A linear regression model is fitted to a dataset (xi, yi) for i = 1, 2, ..., n. Denote by yi the fitted value and by o2 the residual mean squares (i.e., MSRES). (2a) [1 mark] Define the raw residual e; and standardized residual d; using yi, y; and 62. (2b) [1 mark] How do you use di to identify potential outliers? Only stating how, no need to explain. (2c) [1 mark] When plotting e; against the fitted value yi, describe the expected shape of the plot if there are no violations of the model assumptions and no outliers