please explain the right answer and how did we get it

Current Attempt in Progress At December 31, 2020, the trial balance of Sunland contained the following amounts before adjustment Debit Credit 400,000 Accounts Receivable Allowance for Doubtful Accounts Sales Revenue E 1,400 935,400 Your answer is correct. Based on the information given, which method of accounting for bad debts is Sunland using-the direct write-off method or the allowance method? Allowance method (b) (c) Prepare the adjusting entry at December 31, 2020, for bad debt expense, assuming an aging schedule indicates that 11,000 of accounts receivable will be uncollectible. Repeat part (b) assuming that instead of a credit balance there is a 1,400 debit balance in Allowance for Doubtful Accounts During the next month, January 2021, a 2,800 account receivable is written off as uncollectible. Prepare the journal entry to record the write-off. Repeat part (d) assuming that Sunland uses the direct write-off method instead of the allowance method in accounting for uncollectible accounts receivable. (d) (Credit account titles are automatically indented when amount is entered. Do not indent manually) No Account Titles Debit Credit (b) Bad Debt Expense 389.000 Allowance for Doubtful Accounts 389.000 (c) Bad Debt Expense 12400 Allowance for Doubtful Accounts 12400 (d) Allowance for Doubtful Accounts 2.800