Answer and Explanation:
The computation is shown below:
a. Amount of adjusting entry for uncollectible accounts
= Estimated balance of Allowance for Doubtful Accounts + debit balance
= $16,400 + $4,000
= $20,400
b. Adjusted balances
For account receivable
= account receivable
= $420,000
For allowance for doubtful debts
= Estimated amount
= $16,400
For bad debts
= AMount of adjusting entry
= $20,400
c. Net realizable value
= Account receivable balance - estimated balance of Allowance for Doubtful Accounts
= $420,000 - $16,400
= $403,600