A woman sells an average of 300 books per month, with a standard deviation of 50. Over the next ten years, how many months will she sell more than 375 books? (round to the nearest month, if necessary)
Very bad question. I'm struggling particularly with the wording "will she sell".
I suppose the problem wants a z-score $\displaystyle \frac{375-300}{50}$. Determine what probability of the Normal Distribution exceeds this value and calculate the expectation of exceptional sales over 120 months, probably assuming the months are independent.
Yikes! Lots and lots of assumptions in there. Very bad problem. Is she planning to stay in business for the next 10 years?