On January 1, 20X2, Matt and Monica Tire Supply purchased an existing patent on a specialized tire repair tool for $84,000. On January 1, 20X5, the company determined that the invention of a new tool may have diminished the value of its patent. As of January 1, 20X5, Matt and Monica's patent is expected to generate another $61,000 over its remaining legal life, it has a current book value of $58,800, and an estimated fair value of $50,000. 

If the patent is impaired, how much is the impairment loss?