The following figure portrays the appearance of a distribution of efficiency ratings for employees of Nale Nail Works Inc.: Number of ratings 43 58 73 88 103 118 133 148 163 178 193 Efficiency rating a. Estimate the mean efficiency rating. (Round the final answer to 1 decimal place.) Mean efficiency rating b. Estimate the standard deviation. (Round the final answer to the nearest whole number.) Standard deviation c. About 68% of the efficiency ratings are between what two values? (Round the final answers to 1 decimal place.) About 68 % of the efficiency ratings are between 81 and 133 d. About 95% of the efficiency ratings are between what two values? (Round the final answers to 1 decimal place.) About 95% of the efficiency ratings are between and