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 90GPa and 1.8GPa, respectively. Suppose the distribution is normal. (Round your answers to four decimal places.) (a) Calculate P(89x91) 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