On January 1, 2019, the Hogan Manufacturing Company purchased a machine for $250,000. The company expects the service life of the machine to be five years and its anticipated residual value to be $30,000. The companys fiscal year-end is December 31 and the double-declining-balance (DDB) depreciation method is used. Depreciation expense under the DDB method was $60,000 and $100,000 in 2020 and 2019, respectively. During 2021, the company switched from the DDB to the straight-line method. In 2021, the adjusting entry is:

will you please explain how to calculate the double decline depreciation method thank you