how to solve a,b,c,d,e

Researchers are concerned about the impact of students working while they are enrolled in classes, and they'd like to know if students work too much and therefore are spending less time on their classes than they should be. First, the researchers need to find out, on average, how 5 hours. many hours per week students are working. They know from previous studies that the population standard deviation of this variable is about A survey of 200 students provided a sample mean of 7.10 hours worked. What is a 99% confidence interval based on this sample? What distribution did you use to find the confidence interval in part a, and why did you use it? What was the error of the confidence interval you found in part a? .Suppose that one of the researchers found a 95% confidence interval to be 6.82