Castle Company provides estimates for its uncollectible accounts. The allowance for uncollectible accounts had a credit balance of $17,280 at the beginning of 2013 and a $22,410 credit balance at the end of 2013 (after adjusting entries). If uncollectible accounts were charged to the income statement directly instead of through the allowance account, the income statement for 2013 would have included bad debt expense of $17,100 and revenu of $2,200 from the collection of previously written off bad debts. Required: Determine bad debt expense for 2013 according to the allowance method