Two Cal Poly freshmen gathered data on a random sample of textbooks from the campus bookstore in November of 2006. Two of the variables recorded were the price of the book and the number of pages that it contained. These data are in the file TextbookPrices.
a. Identify the explanatory and response variables in this study.

b. Determine the equation of the least squares line for predicting price from number of pages. Report the equation, being sure to use good statistical notation.
c. Use the least squares line to predict the price of a 500-page textbook. Then do the same for a 1,500-page textbook. Which prediction would you have more confidence in? Explain.
d. Interpret what the slope coefficient means in this context.
e. Determine the proportion of variability in textbook prices that is explained by knowing the number of pages in the book.