Ferris company began 2018 with 7,000 units of its principal product. the cost of each unit is $9. merchandise transactions for the month of january 2018 are as follows: purchases date of purchase units unit cost* total cost jan. 10 6,000 $ 10 $ 60,000 jan. 18 7,000 11 77,000 totals 13,000 137,000 *includes purchase price and cost of freight. sales date of sale units jan. 5 3,000 jan. 12 1,000 jan. 20 4,000 total 8,000 12,000 units were on hand at the end of the month. required: calculate january's ending inventory and cost of goods sold for the month using each of the following alternatives: 1. fifo, periodic system. 2. lifo, periodic system. 3. lifo, perpetual system. 4. average cost, periodic system. 5. average cost, perpetual system.