In recent years, Dobbs Company has purchased three machines. Because of a bad employee named Wares in the accounting department, a different accountant was hired to take charge of selecting the depreciation method for each machine. Information concerning the machines is summarized in the table below.

Machine Acquired Cost Salvage Value(in years) Useful Life Depreciation method

1 Jan. 1, 2015 $96,000 $12,000 15 Straight-line

2 Oct. 1,2016 $85,000 $10,000 5 Double-Declining Balance

3 Nov. 1, 2016 $66,000 $6,000 6 Units-of-Activity

For the units-of-activity method, total machine hours are expected to be 30,000. Actual hours of use in the first 3 years were: 2016, 800; 2017, 4,500; and 2018, 7,000.

a) Compute the amount of accumulated depreciation on each machine at December 31, 2018.

b) If machine 2 was purchased on April 1 instead of October 1, what would be the depreciation expense for this machine in 2016? In 2017?