A sample survey of 52 discount brokers showed that the mean price charged for a trade of 100 shares at $50 per share was $33.76. The survey is conducted annually. With the historical data available, assume a known population standard deviation of $15. a. Using the sample data, what is the margin of error associated with a 95% confidence interval (to 2 decimals)? b. Develop a 95% confidence interval for the mean price charged by discount brokers for a trade of 100 shares at $50 per share (to 2 decimals)