Detailed Answer
(b) A change in depreciation method is a change in
method that is not distinguishable from a change in estimate, and
is accounted for as a change in estimate. The change is reported
on a prospective basis in the current year and future years. Book
value as of 1/1/Y3 = $153,600/8 years remaining = $19,200 depreciation
expense in year 3.