17. Scores on a final exam taken by 1,200 students have a bellshaped distribution with mean 72 and standard deviation 9. What is the median score on the exam? About how many students scored between 63 and 81? About how many students scored between 72 and 90? About how many students scored below 54? 9'99\".\" 21. Speeds of vehicles on a section of highway have a bell-shaped distribution with mean 60 mph and standard deviation 2.5 mph. a. If the speed limit is 55 mph, about what proportion of vehicles are speeding? b. What is the median speed for vehicles on this highway? c. What is the percentile rank of the speed 65 mph? d. What speed corresponds to the 16th percentile