In оrder tо determine whether оr not а driver's educаtion course improves the scores on а driving exam, a sample of 6 drivers were given the exam before and after taking the course. The results are shown below. Assume the population of differences is normally distributed. Let d = Score After - Score Before. Driver ScoreAfter the Course ScoreBefore the Course 1 87 83 2 88 89 3 91 93 4 77 77 5 93 86 6 83 79 Compute d-bar.