In a contest, a participant should select at random two questions out of seven questions. There are four easy and three difficult questions. Find the probability that the participant will select one easy and one difficult question. ( Hint. Make notice, that if the participant is selecting two questions "one-after- another", then we should count samples of the type " easy and then difficult" and of the type "difficult and then easy" separately.) 3/7 4/7 3/8 5/7 2/7