i need answer

Holt Developments Ltd. put an asset in service on January 1, 2018. Its cost was $324,000, its predicted service life was six years, and its expected residual value was $32,400. The company decided to use double-declining-balance depreciation. After consulting with the company's auditors, management decided to change to straight-line depreciation in 2020, without changing either the original service life or residual value. Required: a. What is depreciation expense for 2020? Depreciation expense b. Calculate the effect of this change on retained earnings. Retained earnings will by