More sales and profits. Using a statistics program, consider again the relationship between the sales and profits of Fortune 500 companies that you analyzed in Exercise 38.

a) Find a 95% confidence interval for the slope of the regression line. Interpret your interval in context.

b) Last year, the drug manufacturer Eli Lilly, Inc., reported gross sales of $23 billion (that’s $23,000 million). Create a 95% prediction interval for the company’s profits, and interpret your interval in context.