Calculating Cost of Goods Sold and Ending Inventory under Periodic FIFO. LIFO, and Weighted Average In its first month of operations, Literacy for the Illiterate opened a new bookstore and bought merchandise in the following order. 300 units at $7 on January 1, 450 units at $8 on January 8, and 750 units at $9 on January 29. Assuming 900 units are on hand at the end of the month, calculate the cost of goods sold and ending inventory on January 31 under the FIFO, LIFO, and weighted average cost flow assumptions. Assume a periodic inventory system is used