Presented below are two independent situations.

a. On January 6, Arneson Co. sells merchandise on account to Cortez Inc. for $9,000, terms 2/10, n/30. On January 16, Cortez Inc. pays the amount due. Prepare the entries on Arneson's books to record the sale and related collection.

b. On January 10, Mary Dawes uses her Pierson Co. credit card to purchase merchandise from Pierson Co. for $9,000. On February 10, Dawes is billed for the amount due of $9,000. On February 12, Dawes pays $5,000 on the balance due. On March 10, Dawes is billed for the amount due, including interest at 2% per month on the unpaid balance as of February 12. Prepare the entries on Pierson Co.'s books related to the transactions that occurred on January 10, February 12, and March 10.