An advertising firm wishes to demonstrate to its clients the effectiveness of the advertising campaigns it has conducted. The following bivariate data on twelve recent campaigns, including the cost of each campaign (denoted by x, in millions of dollars) and the resulting percentage increase in sales (denoted by y) following the campaign, were presented by the firm. A scatter plot of the data is shown in Figure 1. Also given are the products of the values for campaign cost and values for percentage increase in sales for each of the twelve campaigns. (These products, written in the column labelled "xy," may aid in calculations.)

Campaign cost, X Increase in (in millions of sales, y xy dollars) (percent) 3.99 7.06 28.1694 7.2 3.83 6.89 26.3887 7 - X 1.39 6.60 9.174 X X 1.45 6.37 9.2365 6.8- X X 3.27 6.57 21.4839 6.6- X X X 1.60 6.27 10.032 6.4 X X 2.15 6.44 13.846 X 6.2. 3.00 6.65 19.95 3.54 6.81 24.1074 2.15 6.79 14.5985 1.5 2 2.5 3 3.5 3.05 6.88 20.984 Figure 1 2.16 6.58 14.2128 Send data to calculator V Send data to Excel Answer the following. Carry your intermediate computations to at least four decimal places, and round your answer as specified below. (If necessary, consult a list of formulas.) What is the value of the slope of the least-squares regression line for these data? Round your answer to at least two decimal places