A recent survey reported that the mean total earnings that a worker in Country X can expect to earn between ages 25 and 64 is $1 million for those with only a high school education and $3 million for those with a doctoral degree.

(a) Assuming eight years for a doctoral degree and a straight-line regression of y = total earnings on x = number years of education, what is the slope?

(b) If y instead measures earnings per year (rather than for 40 years), then what is the slope?