ABC Company in Saudi Arabia purchased machinery for SAR 1,000,000 with an estimated salvage value of SAR 100,000 after 5 years of useful life. Calculate the annual depreciation expense using both the straight-line method and the double-declining balance method. Additionally, assume that after 3 years of use, the company decides to dispose of the machinery for SAR 400,000. Determine the gain or loss on disposal and its impact on the company's tax liability if the tax rate is 25%.