A company purchased a building for $1,000,000 on January 1, 2021. The building has a useful life of 40 years and an estimated residual value of $100,000. On December 31, 2021, the company paid $50,000 for a major renovation to the building that extended its useful life by 10 years. The company uses the straight-line method of depreciation. On January 1, 2024, the company decided to change the depreciation method from straight-line to double-declining balance.

a) Calculate the annual depreciation expense of the building for the years 2021, 2022, and 2023.
b) Calculate the carrying value of the building as of December 31, 2023.
c) Calculate the revised annual depreciation expense for the years 2024 and 2025 under the double-declining balance method.
d) Explain why a company might choose to change its depreciation method.