In a class activity, all the 15 students wear hats. 7 students wear red hats, 6 students wear green hats and 2 students wear white hats. (I) two of the 15 students are picked at random. Show that the probability that these two students wear hats of the the same colour is 37/105. (I) three of the 15 students are picked at random. Find the probability that at least 2 of these students wear red hats.