An economist conducted a study of the possible association between weekly income and weekly grocery expenditures. The particular interest was whether higher income would result in shoppers spending more on groceries. A random sample of shoppers at a local supermarket was obtained, and a questionnaire was administered asking about the weekly income of the shopper’s family and the grocery bill for that week. The gender of the shopper was also obtained. The least squares line had a slope of 0.079 . The average amount by which the grocery bill increases for an increase of $100 per week is given by: