On December 31, 2019 Marp Corporation had the following account balances related to credit sales and receivables prior to recording adjusting entries: Account receivable $150,000 credit Allowance for Doubtful Accounts 1,500 debit Sales revenue (all credit sales) 970,000 credit Present the necessary year-end adjusting entry related to uncollectible accounts for each of the following independent assumptions: a) An aging schedule of accounts receivable is completed. It is estimated that $10,000 of the receivables outstanding at year-end will be uncollectible. b) It is estimated that 1.5% of the credit sales will prove to be uncollectible. c) Assume the same information presented in a) above except that prior to adjustment, the Allowance for doubtful accounts had a credit balance of $1,400. d) Assume the same information presented in b) above except that prior to adjustment, the Allowance for doubtful accounts had a credit balance of $1,400