Experience with workers in a certain industry indicates that the time required for a worker to randomly perform a task is distributed in an approximately normal manner, with a standard deviation of 12...

Experience with workers in a certain industry indicates that the time required for a worker to randomly perform a task is distributed in an approximately normal manner, with a standard deviation of 12 minutes. A sample of 25 workers provided an average of 140 minutes. The 95% confidence limits for the arithmetic mean of the population of workers who perform that particular service are:

answer: (135.3; 144,7)