On January 2, 2016, David Corporation purchased a patent for $570,000. The remaining legal life is 10 years, but the company estimated that the patent will be useful only for six years. In January 2018, the company incurred legal fees of $100,000 in successfully defending a patent infringement suit. The successful defense did not change the companys estimate of useful life. Required: Prepare journal entries related to the patent for 2016, 2017, and 2018.