The city transportation department wants to estimate the average number of daily riders for a city-wide bus system. They need to determine the number of people to include in the survey in order to estimate the average to within 25 using a 95% confidence interval. In similar cities, daily ridership ranged from 1500 to 2000. How many people are needed in the survey to meet the requirements?

(Note: "within 50" means as much as 50 more or as little as 50 less. Example: Suppose you are willing to pay $10 for a movie ticket, but you are wiling to pay as much as $12 or as little as $8. Then you would be "within $2" of the original estimate of $10.)