An article in Concrete Research presented data on compressive strength x and intrinsic permeability y of various concrete mixes and cures. Summary quantities are n = 14, Σyi = 572, Σyi² = 23530, Σxi = 43, Σxi² = 157.42, and Σxiyi = 1697.80. Assume that the two variables are related according to the simple linear regression model. a. Use the equation of the fitted line to predict what permeability would be observed when the compressive strength is x = 4.3. b. Give a point estimate of the mean permeability when the compressive strength is x = 3.7. c. Suppose that the observed value of permeability at x = 3.7 is y = 46.1. Calculate the value of the corresponding residual (error). d. Estimate σ². e. Test for significance of regression using α = 0.05. Can you conclude that the model specifies a useful linear relationship between these two variables?