fi rm administers a test to sales trainees before they go into the fi eld. The management of the fi rm is interested in determining the relationship between the test scores and the sales made by the trainees at the end of one year in the fi eld. The following data were collected for 10 sales personnel who have been in the fi eld one year. Salesperson Number Test Score (T) Number of Units Sold (S) 1 2.6 95 2 3.7 140 3 2.4 85 4 4.5 180 5 2.6 100 6 5.0 195 7 2.8 115 8 3.0 136 9 4.0 175 10 3.4 150 (a) Find the least-squares regression line that could be used to