Hi, please help me to figure out this question, thank you!

A statistics practitioner took a random sample of 45 observations from a population whose standard deviation is 21 and computed the sample mean to be 102. Note: For each confidence interval, enter your answer in the form (LCL, UCL). You must include the parentheses and the comma between the confidence limits. A. Estimate the population mean with 95% confidence. Confidence Interval = B. Estimate the population mean with 95% confidence, changing the population standard deviation to 41; Confidence Interval = C. Estimate the population mean with 95% confidence, changing the population standard deviation to 7; Confidence Interval =