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 long-distance calls has changed. Fifty calls, originating from the town, was randomly selected and the following summary minutes. 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.

PLEASE ANSWER C& D ONLY

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 long-distance calls has changed. Fifty calls, originating from the town, was randomly selected and the following summary minutes.
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.