Which of the following errors would cause a trial balance to have unequal totals? Explain your answers.

a. A payment to a creditor was recorded as a debit to Accounts Payable for $129 and as a credit to Cash for $102.

b. A payment of $150 to a creditor for an account payable was debited to Accounts Receivable and credited to Cash.

c. A purchase of office supplies of $420 was recorded as a debit to Office Supplies for $42 and as a credit to Cash for $42.

d. A purchase of equipment for $450 was recorded as a debit to Supplies for $450 and as a credit to Cash for $450.