please solve:

On December 1, Nova company had an inventory of 25 wall clocks at a cost of $20 each. The company uses a perpetual inventory system. During December , the following transactions and events occurred. DEC. 4 Purchased 70 wall clocks at $20 each from Scully, terms 1/10, n/30. DEC. 6 Received credit for the return of 6 wall clocks purchased on DEC. 4 that were defective. DEC. 9 Sold 50 wall clocks for $35 each to Oliver, terms 2/10, n/30. DEC. 13 Sold 15 wall clocks for $40 each to Heathers Supply, terms n/30. DEC. 14 Paid scully in full, less discount. a)Journalize the December transactions for Nova company and post to the ledger account. b) Why is it important to keep purchases of merchandise in a separate account from purchases of office supplies