Engine Central had the following sales transactions in December:

Dec.4Sold $6,700 of merchandise on account to Mo's Motors, terms 2/15, net 30. Cost $3,350.7Mo returned $1,200 of merchandise to Engine Central because he changed his mind and wanted to order a different type of engine. Cost $600.16Mo paid the balance owing to Engine Central.

a. Prepare the journal entries to record the sales transactions on the books of Engine Central using a perpetual inventory system and the earnings approach for revenue recognition.

b. Prepare the journal entries to record the sales transactions on the books of Engine Central using a periodic inventory system and the earnings approach for revenue recognition.