A sample of 10 billionaires is selected, and the person's age and net worth are compared. The data are given here. X (age) 56 39 42 60 84 37 68 66 73 55 Y (net worth in billions) 18 14 12 14 11 10 10 7 7 5 x = 580; y = 108; x2 = 35,780; y2 = 1304; xy = 6120 For the billionaire data, find the y-intercept of the least squares (regression) line