The units of an item available for sale during the year were as follows: Jan. 1 Inventory 21 units at $60 Mar 4 Purchase 29 units at $65 Aug 7 Purchase 10 units at $68 Nov 15 Purchase 15 units at $70 There are 18 units of the item in the physical inventory at December 31. The periodic inventory system is used. Determine the inventory cost and the cost of merchandise sold by three methods . First in first out Last-in, first out Average cost