Alamina occupies the region inside the circle x2 + y2 = 14y but outside the circle x2 + y2 = 49. find the center of mass if the density at any point is inversely proportional to its distance from the origin.

2people are trying different phones to see which one has the better talk time. chatlong has an average of 18 hours with a standard deviation of 2 hours and talk-a-lot has an average of 20 hours with a standard deviation of 3. the two people who tested their phones both got 20 hours of use on their phones. for the z-scores i got 1 for the chatlong company and 0 for talk-a-lot. what is the percentile for each z-score?