The data set cars from Ezekiel (1930) contains stopping distances for various speeds. Smooth the data using Friedman's smoother by choosing your own value of the span. Use dist as the dependent (response) variable and speed as the independent (predictor) variable. Using trial and error, what seems to be a reasonable span? Comment on the graphical comparison between the estimate using your choice of span with the estimate using the span chosen by cross-validation.