6) Three years ago, one division of the Calsone Enterprise Company purchased depreciable assets costing $2,000,000. The cash flows from these assets for the past three years have been: Year Cash flows 1 $ 600,000 2 700,000 3 810,000 Calsone uses the straight-line depreciation method and the assets had an estimated useful life of 10 years with no salvage value. Required: a. What was the ROI for each year using historical cost and gross book value? b. What was the ROI for each year using historical cost and net book value