Rhino Inc. had following property, plant and equipment purchases during 2019: (1) On April 4, equipment costing $250,000 with a 5-year service life and an estimated $40,000 residual value was purchased. (2) On October 4, a machine costing $330,000 with a 5-year service life and an estimated $50,000 residual value was purchased. Assuming Ad Hock has a December 31 year end, prepare the necessary adjusting journal entries at December 31, 2019 to record depreciation under the following depreciation methods (using the nearest whole month method): (a) Straight-line (b) Double-declining-balance