Some nations require their students to pass an exam before earning their primary school degrees or diplomas. A certain nation gives students an exam whose scores are normally distributed with a mean of 41 points and a standard deviation of 9 points. Suppose we select 2 of these testers at random, and define the random variable D as the difference between their scores. We can assume that their scores are independent.
Find the probability that their scores are within 10 points of each other.