The Sun Company accrues bad debt expense during the year at an amount equal to 3% of credit sales. At the end of the year, a journal entry adjusts the allowance for uncollectible accounts to a desired amount based on an aging of accounts receivable. At the beginning of 2015, the allowance account had a credit balance of $18,000. During 2015, credit sales totaled $480,000 and receivables of $14,000 were written off. The year-end aging indicated that a $21,000 allowance for uncollectible accounts was required. What is the Sun Company's bad debt expense for 2015?