Three different companies each purchased trucks on january 1, 2018, for $68,000. each truck was expected to last four years or 200,000 miles. salvage value was estimated to be $6,000. all three trucks were driven 65,000 miles in 2018, 40,000 miles in 2019, 38,000 miles in 2020, and 60,000 miles in 2021. each of the three companies earned $57,000 of cash revenue during each of the four years. company a uses straight-line depreciation, company b uses double-declining-balance depreciation, and company c uses units-of-production depreciation. answer each of the following questions. ignore the effects of income taxes. problem 6-24 part a required a-1. calculate the net income for 2018?