Shown below is activity for one of the products of Denver Office Equipment: January 1 balance, 580 units @ $60 per unit $34,800 Purchases: January 10: January 20: Sales: January 12: January 28: 580 units @ $65 per unit 1,040 units @ $68 per unit 900 units 780 units Required Compute the January 31 ending inventory and costs of goods sold for January, assuming denver uses average cost and a periodic inventory system.