Answer:
$50,000
Step-by-step explanation:
A patent should be recorded at fair market value. When the book value of a patent is higher than its market value, then its book value should decrease. This decrease in the book value is called impairment.
In this case, the patent's book value is $500,000, but its market value is $450,000. The impairment loss = $500,000 - $450,000 = $50,000.