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A random sample of 24 items is drawn from a population whose standard deviation is unknown. The sample mean is x = 870 and the sample standard deviation is s = 25. Use Appendix D to find the values of Student's t. (a) Construct an interval estimate of / with 98% confidence. (Round your answers to 3 decimal places.) The 98% confidence interval is from to (b) Construct an interval estimate of / with 98% confidence, assuming that s = 50. (Round your answers to 3 decimal places.) The 98% confidence interval is from to (c) Construct an interval estimate of / with 98% confidence, assuming that s = 100. (Round your answers to 3 decimal places.) The 98% confidence interval is from to