2. In the multiple regression model y = a + [31x1 + zx2 + 3x3 + u, (1) Briey explain how you can test the hypothesis [31 + 162 = 0. (2) What are the consequences if the correlation between x1 and x3 are very high, say 0.96? (3) Can you identify and estimate all of four parameters if x2 + 4x3 = 3? Be as specific as possible