The Wall Street Journal reported that automobile crashes cost the United States $162 billion annually. The average cost per person for crashes in the Tampa, Florida, area was reported to be $1900. Suppose this average cost was based on a sample of 50 persons who had been involved in car crashes and that the population standard deviation is known to be $500. What is the 90% confidence interval of the average cost per person for crashes in Tampa? What would you recommend if the study required a margin of error of $150 or less?