Allowance for Doubtful Accounts has a credit balance of $900 at the end of the year (before adjustment), and bad debt expense is estimated at 3% of credit sales. If credit sales are $504,100, the amount of the adjusting entry to record the estimated uncollectible accounts receivable

a.is $16,023

b.is $15,123

c.is $14,223

d. cannot be determined.