4.A factory produces socket cap bolts. The mass of socket cap bolts produced by the factory is distributed with a population mean mass of 40 g. From a randomly selected sample of 50 socket cap bolts, a mean mass of 38 g with a sample variance of 58 g2 is obtained. following values:a)The mean of the distribution of sample meansb)The estimated variance of the distribution of sample meansc)The estimated standard deviation of the distribution of the sample means
