Is lack of sleep causing traffic fatalities. A study concluded under the auspices of the National Highway Traffic Safety Administration found that the average number of fatal crashes caused by drowsy drivers each year was 1550. Assume the annual number of fatal crashes per year is normally distributed with a standard deviation of 300.

1. What is the probability of fewer than 1000 fatal crashes in a year?
2. What is the probability of more than 2300 fatal crashes in a year?
3. What is the probability the number of fatal crashes will be between 1000 and 2000 for a year?
4. For a year to be in the upper 5% with respect to the number of fatal crashes, how many fatal crashes would have to occur?

[ I cannot find what formula is used to determine these answers]