A sociology professor assigns letter grades on a test according to the following scheme. A: Top 9% of scores B: Scores below the top 9% and above the bottom 63% C: Scores below the top 37% and above the bottom 24% D: Scores below the top 76% and above the bottom 7% F: Bottom 7% of scores Scores on the test are normally distributed with a mean of 73.9 and a standard deviation of 9.9. Find the numerical limits for a D grade. Round your answers to the nearest whole number, if necessary.