Automobile crashes

The Wall Street Journal reported that automobile crashes cost the United States $162 billion annually (The Wall Street Journal, March 5, 2008). The average cost per person for crashes in the Tampa, Florida, area was reported to be $1599. 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 ? $600. What is the margin of error for a 95% confidence interval? What would you recommend if the study required a margin of error of $150 or less?