Assume I give a test with a mean score of 81 and a standard deviation of 12. Draw a sketch of a normal distribution center at the mean of 81 and divided into five regions based on the following grades: the top 10% of the scores receive an a, the next 20% of the scores received a B, the middle 40% of scores receive a C, the next 20% scores receive a D, the bottom 10% receive an F. Find the minimum scores on the test that would give a student an A, B, C, and D.