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. Campaign cost, x (in millions of dollars) Increase in sales, y (percent) 1.50 6.16 3.57 6.92 3.89 7.00 3.18 6.52 2.10 6.78 3.68 6.76 2.01 6.49 2.82 6.56 1.33 6.39 2.40 6.58 6.96 6.60 Send data to Excel Increase in sales (percent) Campaign cost (in millions of dollars) 2.01 1:46 Send data to calculate The value of the sample.camelation.coefficient r for these data is approximately 0.714 Answer the following Carry your intermediate computations to at least four decimal places, and round your answers as specified below. (If necessary, consult a list of formulas) (a) 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 D