The correct answer to question number one is choice D.
The manager estimates that there are actually $900 in bad debts, but the books only have a balance of $400 in the Allowance for Doubtful Accounts. The entry to adjust it so that the balance will be current is $500 debit to bad debts expense and $500 credit to Allowance for Doubtful Accounts.
The correct answer to question 2 is choice A. Net realizable value is defined as the Gross Accounts Receivable minus the Allowance for Doubtful Accounts.