Assume that the traffic to the web site of Smiley's People, Inc., which sells customized T-shirts, follows a normal distribution, with a mean of 4.5 million visitors per day and a standard deviation of 820,000 visitors per day.

a. What is the probability that the web site has fewer than 5 million visitors in a single day?

b. What is the probability that the web site has 3 million or more visitors in a single day?

c. What is the probability that the web site has between 3 million and 4 million visitors in a single day?

d. Assume that 85% of the time, the Smiley's People web servers can handle the daily web traffic volume without purchasing additional server capacity. What is the amount of web traffic that will require Smiley's People to purchase additional server capacity?