Young's modulus is a quantitative measure of stiffness of an elastic material. Suppose that for metal sheets of a particular type, its mean value and standard deviation are 90 GPa and 2.3 GPa, respectively. Suppose the distribution is normal. (Round your answers to four decimal places.) USE SALT (a) Calculate P(89 X 91) when n = 9. (b) How likely is it that the sample mean diameter exceeds 91 when n = 25? You may need to use the appropriate table in the Appendix of Tables to answer this question.