Human capital theory suggests that those who have invested in higher levels of education will be able to command higher wages. A labour economist collected data on annual wages (Y, in $'000) and years of study (X) from a random sample of 12 employees to test this proposition. Assuming a linear relationship between Y and X, the labour economist used a least-squares method and found that the Y intercept = -23.50 and the slope = 9.73. Also, the sum of squares total (SST) and the error sum of squares (SSE) were equal to 11132.92 and 2406,01, respectively. Based on this information, we can say that a. around 78.39% of the sample variability in Y is due to factors other than X b. around 21.61% of the sample variability in Y is due to factors other than X c. around 21.61% of the variation in Y is explained by the variation in X. d. around 21.61% of the variation in X is explained by the variation in Y