II need help solving in excel

Problem 1: A random sample of 81 students at a local university showed that they work an average of 100 hours per month. The population standard deviation is known to be 27 hours. Answer the 4 questions below. 1) What is the point estimate for the mean hours per month all students at the university work 2) 95% confidence interval is ( D. 3) 99% confidence interval is ( ) Type here which interval is wider. Why