Basic Statistics - Old Questions

3. Under which situations is the Normal distribution used? The annual salaries of employees in a large company are approximately normally distributed with a mean of $50,000 and a standard deviation of $20,000.
(a) What is the probability that people earn less than $40,000?
(b) What is the probability that people earn between $45,000 and $65,000?
(c) What is the probability that people earn more than $70,000? [10]