Periodic inventory using FIFO , LIFO , and weighted average cost methods . The units of an item available for sale during the year were as follows. January 1 Inventory 40 units at $165 $6,600 Aug. 13 Purchased 200 units at $180 , 36,000 Nov 30 Purchase 60 units at $200 12,000 Available for sale 300 units $54,600 . There are 75 units of the item in the physical inventory at December 31 .The periodic inventory system is used a) first in first out FIFO method b) Last in first out ( LIFO ) method C ) Weighted average cost method