STAR-TRACK sells satellite tracking systems for receiving television broadcasts from communications satellites in space. At December 31, 2015, the company's inventory amounted to $44,000. During the first week in January 2016, STAR-TRACK made only one purchase and one sale. These transactions were as follows: Jan. 3 Sold a tracking system to Mystery Mountain Resort for $20,000 cash. The system consisted of seven different devices, which had a total cost to STAR-TRACK of $11,200. Jan. 7 Purchased two Model 400 and four Model 800 satellite dishes from Yamaha Corp. The total cost of this purchase amounted to $10,000; terms 2/10, n/30. STAR-TRACK records purchases of merchandise at net cost. The company has full-time accounting personnel and uses a manual accounting system. Required Prepare journal entries to record these transactions, assuming that STAR-TRACK uses a perpetual inventory system.