Allowance for Doubtful Accounts has a credit balance of $600 at the end of the year (before adjustment), and bad debt expense is estimated at 3% of credit sales. If credit sales are $705,700, the amount of the adjusting entry for the estimated uncollectible accounts receivable a. is $21,771 b. is $20,571 c. is $21,171 d. cannot be determined with the information given