Problem # 3. A recent study of 28 city residents showed that the mean of the time they had lived at their present address was 9.3 years. The standard deviation of the population was 2 years. Find the 90% confidence interval of the true mean? Assume that the variable is approximately normally distributed. Show all your steps.Problem # 4. In a sample of 150 residents, each person was asked if he or she favored the concept of having a single countrywide police agency. The residence (city or outside the city) and the responses of the residents are summarized in the following table. Residence Favor a\") Oppose (A) In City (C ) 80 40 Outside of City (0C) 20 10 If one of these residents is selected at random, a) What is the probability that the person will favor the concept given that the person selected is a city resident? Show all your steps. b) What is the probability that the person will favor the concept given that the person selected is a resident from outside the city? Show all your steps. 0) What is the probability that the person will favor the concept or the person selected is a city resident? Show all your steps. d) What is the probability that the person will favor the concept, or the person selected is a resident from outside the city? Show all your steps