A copy machine dealer has data on the number x of copy machines at each of 89 customer locations and the number y of service calls in a month at each location. Summary calculations give x(bar)=8.4, s(sub x)=2.1, y(bar)=14.2, s(sub y)=3.8, and r=0.86. What is the slope of the least-squares regression line of number of service calls on number of copiers?
(a) 0.86
(b) 1.56
(c) 0.48
(d) None of these
(e) Can't tell from the information given