Calculate the following: 

a. The first year of depreciation on a residential rental building costing $250,000 purchased June 2, 2019.  

b. The second year (2020) of depreciation on a computer costing $5,000 purchased in May 2019, using the half-year convention and accelerated depreciation considering any bonus depreciation taken. 

c. The first year of depreciation on a computer costing $2,800 purchased in May 2019, using the half-year convention and straight-line depreciation with no bonus depreciation. 

d. The third year of depreciation on business furniture costing $10,000 purchased in March 2017, using the half-year convention and accelerated depreciation but no bonus depreciation.