6. A group of 50,000 tax forms has an average gross income of $37,000, with an SD of about $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. What is the chance that between 19% and 21% of the forms chosen for audit have gross income over $50,000? (Show the box model and the result of your work.) Answer: %