Probability statistics... I have NO CLUE what I am doing!

Compensations to chief executive officers of corporations vary substantially from one company tothe next, both in amount and in form. A study showed that that the mean annual salary and bonus compensation to CEOs in 1997 was $634,961 with a standard deviation of $441,690. Assume that annual salaries and bonus compensations are normally distributed.
a.)what is the probability that a randomly seleced CEO received more that $750,000 in 1997?
b.)Explain why the assumption of a normal distribution may be very unlikely.
c.)a sample of 20 CEOs is taken and salaries and bonus compensations are reported. What is the probability that the sample mean salary and bonus compensation falls between $600,000 and $700,000
d.)explain why any normal distrubtion can be used to answer part c with more confidence than part a

If you truly have "no clue", please go have a chat with your academic advisor and please ge retake all the prerequisites for this class.

Did you read the book? Do you have a class? Have you seen even a single example? Yousimply MUST have SOME clue. Please stop thinking like that.

Find a table of the Standard Normal Distribution.
Learn what a z-score is.

That is all you need for Part A.
B requires thinking and formulating of your own opinions based on existing public information.
C requires that you know the difference between a Mean and a Mean of a Sample. Hint: There's a square root in there, somewhere.
D requires you to know something about Confidence and Sample Size and the Law of Large Numbers.

Please get a clue. Then we can talk.