C. 828,571. 21. A company acquires a patent with an expiration date in six years for 100 million. The company assumes that the patent will generate economic benefits that will decline over time and decides to amortize the patent using the double-declining balance method. The annual amortization expense in Year 4 is closest to: A. Y6.6 million. B. 9.9 million. C. 19.8 million. 22. A company is comparing straight-line and double-declining balance amortization meth- ods for a non-renewable six-year license, acquired for 600,000. The difference between the Year 4 ending net book values using the two methods is closest to: A. 81,400. B. 118,600. C. 200,000