4) (40 pts. total) Six students measure a set of hardnesses for a brass specimen and get 49.2, 53.4, 57.8, 54.0, 51.9, 55.5 A) Calculate the mean hardness after annealing. B) Calculate the experimental standard deviation in hardness after annealing. C) Determine the 95% confidence interval for the hardness after annealing. D) Can you say with 95% certainty that a hardness of 54 + 4 is statistically different than your distribution of samples? Explain your answer. Your answer must be consistent with part C