A company prepared its purchases ledger control account, which showed a balance of $15 960. The following items were then discovered. 1 Discounts received of $450 had been entered into the purchases ledger control account as $540. 2 A payment of $720 to a supplier had not been entered in his account. 3 The purchases ledger debit balances carried down totalling $110 had been omitted from the control account. 4 A contra of $170 had been entered in the purchases ledger but not in the purchases ledger control account. What was the correct total of the trade payables?