$1.$ What was the amount of net Accounts Receivable as of December $31,2021?$ As of December $31,2020?$

$2.$ Review the notes to the financial statements and read the note labeled Accounts Receivable, Net and Other in Note $1$Description of Business, Accounting Policies, and Supplemental Disclosures. How does Amazon.com, Inc. estimate losses on receivables? When are receivables written$-$off?

$3.$ Review the notes to the financial statements and read the note labeled Accounts Receivable, Net and Other in Note $1$Description of Business, Accounting Policies, and Supplemental Disclosures. What was the amount of Allowance for Doubtful Accounts as of December $31,2021?$ As o