The housing department in a large city monitors the rent for rent- controlled apartments in the city. The mayor wants an estimate of the average rent. The housing department must deter-mine the number of apartments to include in a survey in order to be able to estimate the average rent to within $ 100 using a 95% confidence interval. From past surveys, the monthly charge for rent- controlled apartments ranged from $ 1,000 to $ 3,500. How many renters must be included in the survey to meet the requirements?