Random sample of 26 items is drawn from a population whose standard deviation is unknown. The sample mean x = 860 and the sample standard deviation is s=20. Use appendix to find the values of student's t.

A) Construct an interval estimate of u(mean) with 95% confidence. (Round answer to 3 decimal places)

B) Construct an interval estimate of u with 95% confidence, assuming that s = 40. (Round answer to 3 decimal places)

C) Construct an interval estimate of u with 95% confidence, assuming that s = 80. (Round answer to 3 decimal places)