Lucy Huang has just finished her first audit assignment. She is now assisting her audit manager, Tom Lucas, in wrapping up the engagement. He has asked Lucy to make a list of all uncleared review notes, to-do items, and audit procedures, and to note for each whether the matter requires more attention, has been resolved (but is not yet noted on file), or is no longer relevant because of other events. Tom has also asked Lucy to go through the files and remove all unnecessary documentation, drafts, and review notes. Lucy is very nervous about this task because she believes her inexperience will mean that she will not be able to distinguish unnecessary from necessary. She has heard that in a famous case in the United States an audit firm was prosecuted because it shredded files that should have been kept. Which of the following documents are unnecessary?

Original account receivable confirmations

Duplicate copy of trial balance

Superseded payables lead sheet

Preliminary audit planning working paper

Final financial statements

Signed management representation letter