The following (x, y) pairs give the advertising dollars (in millions) spent on direct mail and newspaper advertisements respectively for the same years.
(a) Find the line of best fit and the regression coefficient.
(b) Roughly speaking, how do the two expenditures relate to one another?
(c) Do you think that advertising people believe that one of these forms of advertising can substitute for the other. Data: (10.3,17.7), (8.9,16.5), (7.6,14.8), (4.1,8.2), (2.8,5.7), (1.8,3.7).