scores on an exam appear to follow a normal distribution with u = 60 and 0 = 20. The instructor wishes to give a grade of D to students scoring...

scores on an exam appear to follow a normal distribution with u = 60 and 0 = 20. The instructor wishes to give a grade of D to students scoring between the 10th and 30th percentiles on the exam. For what range of scores should a D be given? What percentage of the students will get a D?