Correction of errors — practice question

Anil works as a trader. When he drew up the trial balance on 31 December 2020, the totals did not match. Debits were $5140 more than credits. The mistakes identified later were: 1 The sales account had been undercast by $7100. 2 Sales returns of $520 had been entered as a credit in 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 no entry had been made in the bank charges account. 4 A cheque refund of $600 for insurance overpaid had been posted to the wrong side of the bank account, and no entry had been made in the insurance account.