Question 2 In 2015, the average duration of long-distance telephone calls from a certain town was 3.9 minutes. A telephone company wants to perform a test to determine whether this average duration of...

Do c & d please

Extracted text: Question 2 In 2015, the average duration of long-distance telephone calls from a certain town was 3.9 minutes. A telephone company wants to perform a test to determine whether this average duration of longdistance calls has changed. Fifty calls, originating from the town, was randomly selected and the following summary minutes. Σx= 205 Σ (x- 2 = 56.43 a) Calculate the sample mean, x. b) Calculate the sample standard deviation c) Using the p value approach at the 1% level of significance, test whether the mean duration of long-distance calls from the town had increased. d) Construct the 99% confidence interval for the population mean duration of the long-distance calls from the town.