Trading volume on the New York Stock Exchange has been growing in recent years. For the first two weeks of January 1998, the average daily volume was 646 million shares (Barrons, January 1998). The probability distribution of daily volume is approximately normal with a standard deviation of about 100 million shares. a. What is the probability trading volume will be less than 400 million shares? b. What percentage of the time does the trading volume exceed 800 million shares? c. If the exchange wants to issue a press release on the top 5% of trading days, what volume will trigger a release?