Answer
a) See the plot in explanation
b) r = 0.6348. Moderate correlation between the variables
c) Substantial relationship
Explanation
a) Graphing Advertising cost as the x-variable and Sales as the y-variable, the scatter plot of the given values is:
b) Correlating these data points with a line (shown in black in the above diagram), we get the next parameters:
where r is the Pearson correlation coefficient.
Given that r is between 0.4 and 0.7, then there is a moderate correlation between the variables.
c) A moderate correlation indicates that there is a substantial relationship between the variables