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. 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