According to the Office for National Statistics (ONS), the monthly growth rate in the quantity of goods bought in Great Britain increased by 1.0% in January 2019, after a 0.7% decline in December 2018.

Source: Office for National Statistics, “Retail sales, Great Britain: January 2019,” February 15, 2019.

Following is a random sample of price per piece (£), X, and quantity sold, Y (in thousands):

Price (x) Thousands of Pieces Sold (y)

£6 90 8 60 10 70 9 30 20 100

a. Compute the covariance.

b. Compute the correlation coefficient.