Journalize the entries for the following transactions:
a. Sold merchandise for cash, $12,150. The cost of the merchandise sold was $9,100.
b. Sold merchandise on account, $6,000. The cost of the merchandise sold was $4,000.
c. Sold merchandise to customers who used MasterCard and VISA, $30,780. The cost of the merchandise sold was $20,000.
d. Sold merchandise to customers who used American Express, $17,650. The cost of the merchandise sold was $10,500.
e. Received an invoice from National Credit Co. for $1,900, representing a service fee paid for processing MasterCard, VISA, and American Express sales.