The following data were obtained to establish whether there was a link between restaurant urnover ('000s) and advertising ('000s). Restaurant a b с d e f g Turnover (y) 80 70 100 92 66 58 52 Advertising (x) 10 8 12 11 3 5 7 a. Use the data in the table to calculate the mean of x and the mean of y. [4 marks] b. Use the data in the table to calculate the variance and standard deviation of x and the variance and standard deviation of y. [6 marks] C. Use the data in the table to calculate the covariance of x and y. [4 marks] d. . Calculate the correlation coefficient of x and y and comment on this value. [4 marks]