On January 2, 2018, 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 2020, the company incurred legal fees of $60,000 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 2018, 2019, and 2020. (If no entry is required for a transaction/event, select "No journal entry required" in the first account field.)