The company intends to evaluate the effectiveness of customer service training. The average time spent per customer before the training was 14 minutes. The service manager randomly selects some employees who recently completed the training and measures the time spent per customer. Can the training be considered effective, and has it had the desired impact on the average time? Use a significance level of 5%.

a) Formulate the hypotheses.
b) Choose an appropriate test method and calculate the test statistic.
c) Formulate the null hypothesis rejection rule.
d) Draw a correct conclusion based on the hypothesis test result.
e) Could the null hypothesis also be rejected with a confidence level of 99%? Justify your answer.

The data on the time spent per customer by the selected employees are as follows:
9, 10, 7, 9, 8, 6, 12, 10, 9, 8, 12, 11, 9, 10, 9, 7, 9, 8, 10, 9, 11, 14, 8, 7, 9, 10, 7, 6