Meca Concrete purchased a mixer on January 1, 2016, at a cost of $36900. Straight-line depreciation for 2016 and 2017 was based on an estimated eight-year life and $2100 estimated residual value. In 2018, Meca revised its estimate and now believes the mixer will have a total service life of only six years, and that the residual value will only be $1100. Required: compute depreciation for 2018 and 2019.