Please see the scatter plot attached. The correlation coefficient is zero.
Work Step by Step
The correlation is zero since there are two pairs of differences for the x values and the y values. (For the x-values, there are two values of differences of 10 [40-50 and 60-50] and two values of differences of 20 [30-50 and 70-50].) The same thing happens with the y-values, thus making a correlation of 0.