A random sample of 80 items is drawn from a population whose standard deviation is known to be = 50. The sample mean is 1formula15.mml = 810. (a) Construct an interval estimate for with 98 percent confidence. (Round your answers to 1 decimal place.) The 98% confidence interval is from ______ to ________

(b) Construct an interval estimate for with 98 percent confidence, assuming that = 100. (Round your answers to 1 decimal place.) The 98% confidence interval is from ______to _______

(c) Construct an interval estimate for with 98 percent confidence, assuming that = 200. (Round your answers to 1 decimal place.) The 98% confidence interval is from ______to______