The answer is P20,000. I just need the complete solution.

Aulus Co. bought a patent from Bane Corp. on January 1, 2021, for P300,DOD. An independent consultant retained by Aulus estimated that the useful life is 30 years from the date it was originally acquired by the seller. The patent's carrying amount on Bane's accounting records was P135,000; Bane had originally purchased the patent at a cost of P180,000. What would be the amortization expense to be recorded in the books of Aulus Co. for the year ended 2021 ? l