A professional golf association wants to compare the mean distances traveled by four brands of golf balls when struck by the same driver. Specifically, a robotic golfer uses a driver to hit a random sample of 80 balls (i.e., 20 balls of each brand). Note that the 80 balls are hit in random order. The distance is recorded for each hit, and the results are provided in the file P12_6.XLS. 

a. Is there any indication of differences in the mean distances traveled by the four types of balls? Perform an appropriate statistical test and report a p-value. 

b. Select an appropriate significance level and construct confidence intervals for all pairs of differences between means. Which of these differences, if any, are statistically significant at the selected significance level?