Michaux Ltd. purchased an office building on January 1, 2006, for $450,000. At that time, it was estimated that the building would last for 30 years and would have a residual value of $90,000. Early in 2012, a significant modification was made to the roof of the building at a cost of $30,000. This modification could not be identified as a separate component, but it was believed that it would add an additional ten years to the useful life. As well, it was estimated the residual value would be reduced to $50,000 at the end of the revised useful life. In 2020, due to a collapse in the local property market, the residual value was revised to nil. The useful life, however, was expected to remain as estimated in 2012. The company uses the straight-line method of depreciation.

Required:

a. Calculate the annual depreciation that was charged from 2006 to 2011.

b. Calculate the annual depreciation that was charged from 2012 to 2019.

c. Calculate the annual depreciation that will be charged from 2020 onwards.