I have to make the following adjustment:

"Make any adjustments necessary to the Installation Inventory account for financial statement preparation. The opening installation inventory is $62,400 and the ending installation inventory is $43,200".

The company uses the PERIODIC INVENTORY SYSTEM, so I'm not able to just credit the installation inventory account and record it as an expense. I calculated my cost of goods sold which is $133,903.50. I'm not sure what the adjustment entry would be given that the periodic system doesn't allow you to take the final inventory figure, then compare it to the ledger value for the Inventory account, which has been kept up-to-date during the fiscal period.