Depreciation is always completely irrelevant in DCF investment appraisal question because it is not a cash flow.
You have asked this in the Paper AFM forum, but it is really a very basic Paper MA example. In Paper AFM there will always be both tax and inflation (and much more information to deal with).
I do suggest that you watch my free lectures on this, and it would be best to watch my Paper MA lectures on investment appraisal first.