Please help with steps and formula

1. Suppose you are the head of a research consulting firm and that you have a client that wants to know the population mean for commute times to work for a city they want to establish their new headquarters in. You tell your team of statisticians to find an answer, with a reasonable degree of confidence, for the client based on a sample of commuters from the city. a. Suppose that your team collects a random sample of 100 commuters from the city and records their travel times, and that the sample mean is 35 minutes. Your firm also knows from past experience that the population standard deviation of commute times for that city is 15 minutes. What would the margin of error be at a 90% level of confidence? b. How about at a 95% level of confidence? c. You decide to present your findings with the confidence interval based on the higher confidence level. What would you show them and how would you explain this confidence interval to the client