in detail please explaining why.

15.2 A supplier sends you a statement showing a balance outstanding of $14,350. Your own records show a balance outstanding of $14,500. Which one of the following could be the reason for this difference? The supplier sent an invoice for $150 which you have not yet received. The supplier has allowed you $150 cash discount which you had omitted to enter in your ledgers. You have paid the supplier $150 which he has not yet accounted for. You have returned goods worth $150 which the supplier has not yet accounted for. (2 marks