Gandolfi Construction Co. purchased a CAT 336DL earth mover at a cost of $515,000 in January 2019. The company's estimated useful life of this heavy equipment is 20 years, and the estimated salvage value is $94,000. Required: a. Using straight-line depreciation, calculate the depreciation expense to be recognized for 2019, the first year of the equipment's life, and calculate the equipment's net book value at December 31, 2021, after the third year of the equipment's life. Depreciation expense Net book value 21,050 493,950 $ b. Using declining-balance depreciation at twice the straight-line rate, calculate the depreciation expense to be recognized for 2021, the third year of the equipment's life. Double-declining rate Depreciation expense