A company does a major upgrade ($10,000) to a building that is expected to extend the useful life of the building.

Data for building before the upgrade:

Cost $100,000

Accumulated Depreciation $20,000

What is the journal entry to record the upgrade?

The correct answer is Debit Accumulated Depreciation $10,000, Credit Cash $10,000, however, I need to know the reasoning behind why we debit accumulated depreciation instead of inventory for example.