Can someone explain why the answer is c???

Broadway Corporation was granted a patent on a product on January 1, 2004. To protect its patent, the corporation purchased on January 1, 2015 a patent on a competing product which was originally issued on January 10, 2011. Because of its unique plant, Broadway Corporation does not feel the competing patent can be used in producing cost of the competing patent should be amortized over a maximum period of 20 years amortized over a maximum period of 16 years amortized over a maximum period of 9 years expensed in 2015