Answer: $2700
Explanation: Under the LIFO inventory method the transactions are recorded on the basis that goods which are most frequent purchase are also sold first. Under the periodic inventory method the accounts are updated at a specific point , generally month end, and not on continuous basis like in perpetual system.
so the cost of goods sold of 450 units will be at latest prices,thus :-
COGS = (450 units)*($6) = $2700