Correction of errors — practice question

Anil is a trader. The totals on the trial balance he prepared on 31 December 2020 failed to agree. Debit totals were $5140 greater than credit totals. The following mistakes were later found. 1 The sales account had been undercast by $7100. 2 Sales returns of $520 had been posted as a credit to the purchases account. The correct entry had already been made in the customer’s account. 3 Bank charges of $320 had been entered correctly in the cash book, but had not been entered in the bank charges account. 4 A cheque refund of $600 for insurance overpaid had been recorded on the wrong side of the bank account and no entry had been made in the insurance account.