With individual lines at its various windows, a post office finds that the standard deviation for normally distributed waiting times for customers on Friday afternoon is 7.2 minutes. To test this claim, the post office experiments with a single, main waiting line and finds that for a random sample of 25 customers, the waiting times for customers have a standard deviation of 3.5 minutes. a) With a significance level of 5 percent, conduct an appropriate test on the claim. (State your null hypothesis, test statistic, critical value, decision rule, conclusion) (15 points) b) What is the 95% confidence interval for the population variance