An equipment bought by XYZ Printing Press that cost P40,000 has a useful life of 4 years and a salvage value of P5000. The equipment can produce 1000 units for the first year, 2000 units for the second year, 3000 units for the third year, and 4000 units for the fourth year. If the units produced are in uniform quality, what is the depreciation charge at the end of the fourth year