Using a perpetual system, how do I determine the FIFO,LIFO, weighted average, and specific identification.

To determine the costs assigned to the December 31 ending inventory using the FIFO (First-In, First-Out), LIFO (Last-In, First-Out), weighted average, and specific identification methods, here's what you need to do:

1. FIFO (First-In, First-Out):
- In FIFO, you assume that the first items purchased are the first ones sold. Therefore, the cost of the ending inventory is based on the latest purchases.
- Calculate the cost of goods sold (COGS) for the 15 units sold on December 15 using the FIFO method:
- 8 units from the December 7 purchase: 8 units x $6.00 per unit = $48.00
- 7 units from the December 14 purchase: 7 units x $12.00 per unit = $84.00
- COGS = $48.00 + $84.00 = $132.00
- Calculate the ending inventory cost by subtracting the COGS from the purchases after December 15:
- 17 units remaining from the December 14 and December 21 purchases: 17 units x $14.00 per unit = $238.00

2. LIFO (Last-In, First-Out):
- In LIFO, you assume that the last items purchased are the first ones sold. Therefore, the cost of the ending inventory is based on the earliest purchases.
- Calculate the COGS for the 15 units sold on December 15 using the LIFO method:
- 7 units from the December 14 purchase: 7 units x $12.00 per unit = $84.00
- 8 units from the December 7 purchase: 8 units x $6.00 per unit = $48.00
- COGS = $84.00 + $48.00 = $132.00
- Calculate the ending inventory cost by subtracting the COGS from the purchases after December 15:
- 17 units remaining from the December 21 purchase: 17 units x $14.00 per unit = $238.00

3. Weighted Average:
- In the weighted average method, you calculate the average cost per unit of all items purchased, including those sold and in the ending inventory.
- Calculate the weighted average cost per unit:
- Total cost for all purchases: (10 units x $6.00 per unit) + (20 units x $12.00 per unit) + (15 units x $14.00 per unit) = $336.00
- Total units purchased: 45 units
- Weighted average cost per unit = $336.00 / 45 units = $7.47 per unit
- Calculate the COGS for the 15 units sold on December 15 using the weighted average cost per unit:
- COGS = 15 units x $7.47 per unit = $112.05
- The ending inventory cost is determined by multiplying the remaining units by the weighted average cost per unit:
- 30 units remaining from the December 14 and December 21 purchases: 30 units x $7.47 per unit = $224.10

4. Specific Identification:
- In specific identification, you identify which specific units were sold and consider their individual costs.
- Since the specific units sold are provided (8 from Dec. 7 purchase and 7 from Dec. 14 purchase), you can simply calculate the total cost of the sold units using their respective costs:
- 8 units from Dec. 7 purchase: 8 units x $6.00 per unit = $48.00
- 7 units from Dec. 14 purchase: 7 units x $12.00 per unit = $84.00
- COGS = $48.00 + $84.00 = $132.00
- The ending inventory cost is calculated by multiplying the remaining units by their respective costs:
- 17 units remaining from the December 21 purchase: 17 units x $14.00 per unit = $238.00

Therefore, the costs assigned to the December 31 ending inventory for each method are as follows:
- FIFO: $238.00
- LIFO: $238.00
- Weighted Average: $224.10
- Specific Identification: $238.00