I need help with this problem, please can you explain step by step

16. (10 points) Write down Excel formulas based on the requirements. (a) (5 points) Suppose we want to stratify the annual income of people into three levels: Low (0~ $40,000), Medium ($40,000~$100,000) and High (> $100,000). Please nish the formulas in Cell C5, which can also be generalized to Cell C6. A A B c 1 Level 2__ 1 _ 150000 High 3 30000 Low 4_ 3 75000 Medium 5 4 85000 6 5 120000 . (b) (5 points) Suppose X follows a normal distribution with mean ,u = 20 and variance 0'2 = 100, E I F Annual Income Level I 0 Low 40000 Medium J 100000 High please write Excel formulas to calculate the probability that X is less than 10 or greater than 30