At the beginning of 2020, the allowance account had a credit balance of $18,000. During 2020, credit sales totaled S480,000 and receivables of $14,000 were written off the year end aging indicated that a $21,000 allowance for uncollectible accounts was required. Bad debt expense for 2020 would be O $17,000 $26,000 $21,000 $14,400