On January 2, 2016, David Corporation purchased a patent for $480,000. 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 $60,00 in successfully defending a patent infringement suit. The successful defense did not change the company's estimate of useful life. Prepare journal entries related to the patent for 2016, 2017, and 2018. (If no entry is required for a transaction/event, select "No journal entry required" in the first account field.)