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 in millions of dollars and the resulting percentage increase in sales following the campaign were presented by the firm Based on these data we would compute the least squares regression line to be y 6 15 0 20x with x representing campaign cost and y representing the resulting percentage increase in sales This line is shown below along with a scatter plot of the data Campaign cost x in millions of dollars 1 76 1 61 1 27 2 25 2 85 3 50 3 73 1 87 2 15 3 89 3 03 3 17 Send data to calculator Increase in sales y percent 6 53 6 25 6 31 6 70 6 65 6 83 6 73 6 83 6 52 7 04 6 93 6 62 Increase in sales percent Based on the firm s data and the regression line complete the following X x x Campaign cost in millions of dollars X a For these data values for percentage increase in sales that are less than the mean of the values for percentage increase in sales tend to be paired with values for campaign cost that are Choose one the mean of the values for campaign cost b According to the regression equation for an increase of one million dollars in advertising campaign cost there is a corresponding increase of how many percent in sales X o E