Which of the following errors, considered individually, would cause trial balance to be unequal

a. Cash received from a customer on account was posted as a credit of 220 to cash and a debit of 220 accounts receivable

b. A payment of 76 for supplies was posted as a debit 67 to supplies expense and a credit 76 to cash

c. A payment of 391 to a creditor was posted as a debit of 931 to accounts payable and credit cash 931

d. A receipt of 252 from customer was posters as a debit of 225 to cash and a credit of 225 accounts receivable