WE have been using a 10 year total useful life on a patent which has been employed for 5 years.WE had purchased it immediately after it was granted from another company for P20,000 which was the only cost relevant to the patent.At the very beginning of Year 6, WE successfully defended it at a cost of P26,000 and decided to change the total useful life to its legal life.What is the amortization of patent in Year 6?