On average, 4% of total accounts receivable has been uncollectible in the past. At the end of the year, the balance of accounts receivable is $120,000 and the allowance for doubtful accounts has an unadjusted credit balance of $600. It is estimated that 4% of credit sales are uncollectible, credit sales during the year were $170,000.

Using the aging of accounts receivable method, the estimated bad debt expense would be: