please help with this is one ,with just answers .

Holt Developments Ltd. put an asset in service on January 1, 2021. Its cost was $288.000, its predicted service life was six years, and its expected residual value was $28,800. The company decided to use double-declining-balance depreciation. After consulting with the company's auditors, management decided to change to straight-fine depreciation in 2023, without changing either the original service life or residual value. Required: a. What is depreciation expense for 2023 ? b. Calculate the effect of this change on retained eamings