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A random sample of 12 shearing pins was taken in a study of the hardness of the head of the pin. Measurements were made for each of the 12, yielding and average of 48.50 kN with a standard deviation of 1.5 kN. Construct a 90 per cent confidence interval of the following: A. Variance of the hardness of all shearing pins. B. Standard deviation of the hardness of all shearing pins