Prior to being hired, the five salespersons for a computer store were given a standard sales aptitude test. For each individual, the score achieved on the aptitude test and the number of computer systems sold during the first 3 months of their employment are shown here.

John    Cora    Sam   Cindy     Henry

x = Score on aptitude test  80  70  45  90  20

y = Units sold in 3 months  25  15  10  40  5

Determine the least-squares regression line and interpret its slope. Estimate, for a new employee who scores 60 on the sales aptitude test, the number of units the new employee will sell in her first 3 months with the company.