I need a walk through on how to answer this question. I got it wrong on a quiz. I just don't know how to do it. I need to know 1st, how I know what formula's to use, then 2nd, how to apply them. I'm completely lost, so I need a step by step. This is the question:

A group of 50,000 tax forms has an average gross income of $37,000, with an SD of $20,000. Furthermore, 20% of the forms have a gross income over $50,000. A group of 900 forms is chosen at random for audit. To estimate the chance that between 19% and 21% of the forms chosen for audit have gross incomes over $50,000, a box model is needed.

a. Should the number of tickets in the box be 900 or 50,000

b. Each ticket in the box shows i or ii, which one? i. a zero or one ii. a gross income

c. True or false: the SD of the box is $20,000.

d. True or false: the number of draws is 900.

e. Find the chance (approximately) that between 19% and 21% of the forms chosen for audit have gross incomes over $50,000.

f. With the information given, can you find the chance (approximately) that between 9% and 11% of the forms chosen for audit have gross incomes over $75,000? Either find the chance or explain why you need more information.