Journalize the entries for the following transactions:

a. Sold merchandise for cash, $6,900. The cost of the merchandise sold was $4,830.

b. Sold merchandise on account, $7,500. The cost of the merchandise sold was $5,625.

c. Sold merchandise to customers who used MasterCard and VISA, $10,200. The cost of the merchandise sold was $6,630.

d. Sold merchandise to customers who used American Express, $7,200. The cost of the merchandise sold was $5,040.

e. Paid an invoice from City National Bank for $675, representing a service fee for processing MasterCard and VISA sales.

f. Received $6,875 from American Express Company after a $325 collection fee had been deducted.