Mechanic

The logic goes...

COGS = cost of purchasing of the goods sold during the period. To find out the net overall purchases, you need to consider the movement in the inventory accounts.

Beginning inventory = $14,000 of stock.

Ending inventory = $10,000 of stock, so, $4,000 of beginning inventory was sold and never replaced through purchases.

Therefore purchases = COGS - $4,000 = $76,000.

The reverse would apply if ending was $14,000 and beginning was $10,000. An additional $4,000 was purchased and not sold, therefore, purchases equal COGS + $4,000.