A random sample of 13 items is drawn from a population whose standard deviation is unknown. The sample mean is @ = 950 and the sample standard deviation is s = 10. Use Appendix D to find the values of Student's t. (a) Construct an interval estimate of / with 99% confidence. (Round your answers to 3 decimal places.) The 99% confidence interval is from to (b) Construct an interval estimate of // with 99% confidence, assuming that s = 20. (Round your answers to 3 decimal places.) The 99% confidence interval is from to (c) Construct an interval estimate of // with 99% confidence, assuming that s = 40. (Round your answers to 3 decimal places.) The 99% confidence interval is from to