3. (6 Points) Given the linear regression equation: y = 1.6 + 3.5x1 - 7.9x2 + 2.0X3 a. (1 Point) Which variable is the response variable? How many explanatory variables are there? b. (1 Point) If x1 = 2, x2 = 1 and x3 = 5, what is the predicted value for y? c. (2 Points) Supposed the n = 12 data points were used to construct the given regression equation above, and that the standard error for the coefficient x, is 0.419. Construct a 90% confidence interval for the coefficient of x1. d. (2 Points) Using the information from part (c) and 5% level of significance. test the claim that the coefficient of x1 is different from 0. What does your conclusion mean in relation to x1 predicting y