DEF Enterprises sold a patent for $10,000. The patent was purchased for $20,000 and had accumulated amortization of $15,000. Requirements: a. Prepare the journal entry to record the sale of the patent. b. Determine the gain or loss on the sale of the patent. c. Record the accumulated amortization. d. Calculate the book value of the patent at the time of sale. e. Analyze the impact of the sale on the income statement and balance sheet.