The variable lintst (the log distance from the nearest interstate highway) has to this point been included as a linear component of the regression. Suppose we included a quadratic term. That is, we add to Model 2 the variable lintst^2.

In a clearly written paragraph, tell me a) what you would predict for the signs of the coefficients on the variables lintst and lintst^2, respectively and b) why you think those predictions make sense. (Hint: would you want to live right next to an interstate highway?)

(Points depend on the quality of your answer. I have a specific answer in mind, but if you give an answer substantially different from that, you can get credit if you make a well articulated, plausible argument.)