Tried to solve this but not sure if I did it correctly. Is it Book

Value at the end of 2020 minus Sale Price or Sale Price minus Book Value at the end of 2020?

Adelphi Company purchased a machine on January 1, 2017, for $50,000.  The machine was estimated to have a service life of ten years with an estimated residual value of $5,000.  Adelphi sold the machine on January 1, 2021 for $28,000. Adelphi uses the double declining method for depreciation. Using this information, how much is the gain or (loss) for the equipment sale entry made on January 1, 2021. Enter a loss as a negative number.