An english professor assigns letter grades on a test according to the following scheme. a: top 14%14% of scores b: scores below the top 14%14% and above the bottom 57%57% c: scores below the top 43%43% and above the bottom 24%24% d: scores below the top 76%76% and above the bottom 8%8% f: bottom 8%8% of scores scores on the test are normally distributed with a mean of 69.669.6 and a standard deviation of 99. find the numerical limits for a d grade. round your answers to the nearest whole number, if necessar