The following data represent the price of a random sample of used Chevy Camaros by age.

(a) Determine the least-squares regression equation, treating age as the explanatory variable.
(b) A normal probability plot of the residuals indicates that the residuals are approximately normally distributed. Test whether a linear relation exists between age and price at the a = 0.05 level of significance.
(c) Plot the residuals against the explanatory variable, age.
(d) Does a linear model seem appropriate based on the scatter diagram and residual plot?