need help on why i got it wrong

At the end of the current year, Accounts Recelvable has a balance of $415,000; Allowance for Doubtful Accounts has a debit balance of $3,500; and sales for the year total $1,870,000. Using the aging method, the balance of Allowance for Doubtful Accounts is estimated as $18,600 a. Determine the amount of the adjusting entry for uncollectible accounts. M. b. Determine the adjusted balances of Accounts Recelvable, Allowance for Doubtful Accounts, and Bad Debt Expense. c. Determine the net realizable value of accounts receivable