Refer to the information presented in Mini-Exercise. Assume that Gandolfi Construction Co. calculated depreciation expense for the CAT 336DL earth mover on the straight-line method and reported $600,000 of net in-come for the year ended December 31, 2016. The company's average total assets for 2016 were $4,000,000.

Required:

a. Calculate Gandolfi's ROI for the year ended December 31, 2016.

b. Calculate what Gandolfi's ROI would have been for the year ended December 31, 2016, had the company used the double-declining-balance depreciation method for the CAT 336DL earth mover.