The accounting records of Metlock Electronics show the following data.

Beginning inventory 2,700 units at $5

Purchases 7,000 units at $7

Sales 8,100 units at $10

1a. Determine cost of goods sold during the period under a periodic inventory system using the FIFO method.

1b. Determine cost of goods sold during the period under a periodic inventory system using the LIFO method.

1c. Determine cost of goods sold during the period under a periodic inventory system using the average-cost method.