Please solve them step by step

7.2.3) A synthetic fiber used in manufacturing carpet has tensile strength that is normally distributed with mean 15.5. psi and standard deviation 3.5 psi. What is the standard deviation of the sample mean when the sample size is (a) n = 10 and (b) n = 45. 7.2.8) Scientists at the Hopkins Memorial Forest in Western Massachusetts have been collecting meteorological and environmental data in the forest for more than 100 years. In the past few years, sulfate content in water samples from Birch Brook has averaged 15 mg/L with a standard deviation of 1.5 mg/L. (a) What is the standard error of the sulfate in a collection of 15 water samples? (b) If 15 students measure the sulfate in their samples, what is the probability that their average will be between 5.75 and \"35 mglL? (e) What do you need to assume for the probability calculated in (b) to be accurate