Swifty Corporation began operations on December 1, 2019. The only inventory transaction in 2019 was the purchase of inventory on December 10, 2019, at a cost of $21 per unit. None of this inventory was sold in 2019. Relevant information is as follows. Ending inventory units December 31, 2019 December 31, 2020, by purchase date: December 2, 2020 July 20, 2020 120 120 50 170 During the year 2020, the following purchases and sales were made. Purchases Sales March 15 July 201 320 units at $26 April 10 220 320 units at 27 August 20 320 September 4 220 units at 30 November 18 170 December 2 120 units at 32 December 12 220 The company uses the periodic inventory method.